Virtually all the correspondence prior to 1819 concerns Abiel Leonard's father, Nathaniel Leonard, Sr., who was a recruiter in the army of the United States. From 1798 to1805 the correspondence relates primarily to military matters such as payment for finding deserters, and obtaining clothing and other supplies for soldiers. There are also a few items from Nathaniel's brother, Phillip, who was in the navy.

Beginning in 1819 the focus switches to Abiel Leonard's life. During the 1820s there are several letters from his brother, Nathaniel, Jr., from New England and Chicago, prior to his settling in Missouri. There are also letters from his parents, often concerning financial problems and requests for assistance, and a few from his sister Margaret and her husband Jonathan Bailey, and sister Mary and husband Jonathan Bell. The 1820s correspondence also begins to relate to Leonard's legal career, primarily working with estate settlements and as a collection agent for debts. Of special interest is some correspondence relating to a duel fought with Taylor Berry in 1824, for which Leonard was tried and fined $150.

There is also correspondence relating to the official 1825 survey of the Santa Fe Trail. Benjamin Reeves was one of the three commissioners appointed by the president of the United States to survey the road. Reeves would later become Abiel Leonard's father-in-law, thus some of his correspondence is included here as part of the family papers. These include a memo book, trail diary, accounts, and several very interesting letters to Reeves from George Sibley, one of the other commissioners.

From the 1830s on, the Correspondence series provides a wonderful insight into the life of a prominent mid-Missouri lawyer and businessman and his family. Because Abiel Leonard spent so much time apart from his family and he insisted upon frequent communication with even the youngest of his children, there is a wealth of letters describing household obligations, educational pursuits, social activities, relations with slaves and other servants, and various other issues relating to family life in a well-to-do nineteenth century home and a small plantation. Letters between Abiel and his wife Jeanette, although often containing lists of specific instructions and admonitions, also include affectionate allusions. Those with the children consist primarily of descriptions of educational endeavors and suggestions of further pursuits.

Brother Nathaniel Leonard, Jr., who settled in Cooper County, Missouri, was a frequent correspondent throughout his life. His letters consist of information about family events and about his business activities, including raising livestock such as cattle, hogs and mules, and agricultural crops like corn and hemp. He also frequently asks his brother's advice about engaging in land speculation.

There continues to be a considerable amount of correspondence relating to Leonard's legal profession through the 1840s and into the 1850s. There are significant changes in the types of cases discussed and the obviously increased respect of the correspondents for Leonard's legal opinions. When reading the legal correspondence, researchers should be also be aware that there may be related material in the Legal Records series.

Throughout the entire series are letters rife with the political opinions of the period, both local and national. Most of the politicians in Missouri during the mid-nineteenth century either corresponded with Abiel Leonard themselves, or were discussed by their friends and/or enemies in their correspondence. Opinions about Henry Clay, Zachary Taylor, and other national figures are discussed as well.

During the mid- to late 1850s correspondence from Reeves and Ada, then Kate, from their schools on the East Coast, give some idea of the social life and educational activities of upper class youth of the period. They discuss expenses and living arrangements and, particularly in the case of Reeves at Dartmouth, their educational courses.

The Leonard family was also quite religious and there are frequent mentions of church services, opinions of sermons, and recruiting and supporting clergy. The family usually attended Episcopalian services when available, but if that was not possible, they attended services of other denominations. There is mention of helping to support Central [Methodist] College in Fayette.

Politics continues to be a frequent topic of discussion, with Leonard expressing opinions about slavery in Nebraska Territory in 1854. Several letters in the late 1850s and early 1860s allude to the national strife and the election of 1860. Other correspondence in the 1850s from son-in-law Horace Everett, brother Nathaniel, and others, consists primarily of discussions of real estate speculation.

Reeves Leonard returned from his studies in Germany around the start of the Civil War. He enlisted as a captain, and was later promoted to major, in the Missouri State Militia, fighting for the Union cause. The correspondence during the war years, though not extensive, includes discussion of emancipation, runaway slaves, contraband, bushwhacker raids, and some military correspondence. Abiel's death in 1863 is noted by resolutions of the Bar of Fayette.

After the war, much of the correspondence relates to Reeves' attempts to settle his father's estate by selling off land. There are also letters from his sisters about family matters, Mary in Council Bluffs, Iowa; Martha in St. Joseph; Kate in Columbia; Ada back home with Jeanette after the death of her husband, Bishop Hawks; and from his brothers at school, Abiel, Jr. at Dartmouth and theology school in New York, and Willie in St. Louis and at Dartmouth. By 1869, when the estate appears to be in better shape, the correspondence shows that Reeves often makes a business of loaning money at interest from the estate. The 1870s include about equal amounts of business (mostly land transactions and loans) and family correspondence.

With the death of Reeves Leonard in 1878, the amount of correspondence decreases considerably and consists almost entirely of Willie's business transactions. The undated correspondence includes several letters written by Nathaniel about land purchases and farming; notes relating to, or drafts of Abiel's speeches, judicial opinions and decisions; and various family missives, especially from Martha, who seldom dated her correspondence.

Seventeen letterbooks, written by Abiel Leonard and dated 1827-1852, contain copies of his outgoing business correspondence. Early volumes contain material about his legal cases, some with lengthy explanations of the laws behind the opinions. Some later letters also discuss legal cases, but most consist primarily of business matters, including lands acquired, loans made, and collecting debts. There appear to be one or two volumes missing for the year 1843.

Notebooks entitled "memorandum books" by Leonard, dated 1823-1851, and undated, conclude the correspondence series. They contain notes about cases in various circuit courts, a docket of Missouri Supreme Court cases, and memos relative to New Madrid titles. There are also detailed accounts of collecting debts and rents for clients, as well as personal accounts.

The Legal Records series consists of legal documents arranged chronologically, 1782-1894, and undated; legal notebooks, 1820-1856; and Leonard's legal cases, arranged in alphabetical order, with several folders of cases related to New Madrid claims listed alphabetically at the end of the legal cases subseries.

The legal documents relate primarily to Leonard's clients, but do include personal and family documents, as well. They consist of contracts, deeds, wills, estate lists, land grants and other land records, bills of sale, depositions, and other notes and papers relating to his cases.

Of particular interest are some 1821 deeds and contracts relative to setting aside land in Columbia for the university, in Cole County for a courthouse and jail, and in Cote Sans Dessein to locate the state capital. Although the majority of documents in this section concern cases relating to debt collection, land transactions, estates, and other financial-type matters, there are also notes and depositions about cases such as an indentured 12-year-old, who had been apprenticed to learn a trade, suing his master for not teaching him, 1836; the mistreatment and death of a female slave, 1839; the rape of a schoolgirl, 1840; a prenuptial contract, 1842; spousal abuse, 1849; and an 1868 contract to hire a 10-year-old servant girl until she turns 14, in return for teaching her to read and write.

Several legal notebooks, 1820-1856, consist of Leonard's notes concerning many of his cases. Researchers should note that the material in these volumes also might relate to items in the legal documents and legal cases subseries, as well as in the correspondence series. Thorough investigation of a legal case may require examination of items from all of the subseries for the time period in question.

The legal cases subseries is arranged alphabetically and, for the most part, has been kept in the order originally placed by an earlier processor. The subseries consists of notes, depositions, and correspondence. Most of the cases concern suits for collection of payment of debt and other financial disputes. Other types of cases, involving manslaughter, murder, assault, slander, embezzlement, slave ownership, etc., are noted. Cases specifically related to New Madrid claims are arranged alphabetically at the end of the other legal cases. Of special interest are the 1828 Missouri House and Senate impeachment proceedings against Judge David Todd for willful misconduct.

The Business Records series consists of account books, dated 1822-1878, and business documents, arranged chronologically from 1792 to 1909, and undated.

The account books identified by Leonard as "Private Accounts," up to his death in 1863, are very comprehensive, covering both private and professional transactions—including lists of clients, the service Leonard performed, and the fee charged. They provide a unique view of the business workings of a law practice in the early to mid-nineteenth century. Leonard was also scrupulous about keeping records of his own private business dealings and personal accounts. Details of personal loans, home construction and improvements, domestic expenses and purchases, etc., provide a glimpse of the financial workings of an upper-class family of the 1800s. There are a few other books, interfiled chronologically, in which Leonard kept a separate record of specific accounts, particularly in the early years when much of his practice involved dealing with collections for clients. Jeanette Leonard's accounts are included in the last couple of volumes, but are not nearly as detailed as those of her husband.

The Business Documents subseries includes bills, receipts, and listings of income and expenditures. Of particular interest may be a list of expenditures and copies of accounts of the Santa Fe Trail Commission survey, 1825-1826 (f. 1034-1035); bills for items to set up a newlywed household, 1831 (f. 1041); list of slaves for sale, 1845 (f. 1085); and several pages of notes and diagrams related to the building of a house, 1850 (f. 1101). The documents provide unique insight into the financial situation of a mid-nineteenth century family. Receipts and bills for general merchandise, dry goods, furniture, building supplies, books, and livestock, and for services such as education, carpentry, masonry, blacksmithing, medical care, dentistry, sewing, shoemaking, etc., provide documentation of the costs of these goods and services during the period.

A large portion of the documents throughout the subseries, but especially after Abiel Leonard's death, concern tax records of the extensive land holdings of Leonard and his estate. The documents from 1898 to 1909 relate almost exclusively to distributions from his estate to his heirs.

The Military Documents series is arranged chronologically from around the late 1790s to 1865, and consists primarily of muster rolls and general orders, 1790s and early 1800s; and poll books of elections of the Missouri Militia, late 1820s and early 1830s. (Abiel Leonard was appointed Judge Advocate of the First Brigade, First Division of the militia in 1826.); and documents of Reeves' military service in Company A, 9th Cavalry, Missouri State Militia during the Civil War, including enlistment records, return of quartermaster stores, inventories of effects of deceased soldiers, receipts for forage, etc.

The Miscellaneous series consists of Leonard's notes for political speeches, Leonard family genealogy and photographs, plat maps of mid-Missouri towns, some 1832 Spanish language documents relating to Santa Fe, and several folders of undated schoolwork, including translations from Latin and Greek classics, compositions, poetry, and sermon notes.