After Kentucky gained statehood in 1792, Marshall was elected to the state legislature despite the fact that he was a Federalist and zealously antireligious – both of which made him unpopular with many Kentuckians.

The Federalist cause received a slight boost when federal forces were successful in quashing the Whiskey Rebellion and ending the Indian threat at the Battle of Fallen Timbers.

As a senator, Marshall clung to Federalist principles, supporting the Alien and Sedition Acts and voting to ratify the Jay Treaty.

His allegations resulted in a legislative investigation of Kentucky Court of Appeals judge Benjamin Sebastian, who was found to be receiving a pension from Spain and resigned from the bench.

Federal judge Harry Innes was also a target of Marshall's allegations, and the two became embroiled in a legal battle that lasted almost a decade.

[3] Little is known of Marshall's early years, but one tradition holds that he had no formal education during his childhood and that his cousin Mary (later, his wife) taught him to read.

[1] On January 4, 1778, Marshall enlisted as a cadet for a three-year term in the Virginia State Regiment of Artillery for service in the Revolutionary War.

[8] In 1782, Marshall moved to present-day Kentucky and became deputy surveyor of Fayette County, again serving under his uncle Thomas.

[8] According to tradition, Marshall was known to boast that he could ride from Frankfort to Versailles, a distance of some 20 miles (32 km), and never enter a tract of land that he didn't own.

[12] A 1788 letter in the Kentucky Gazette indicated that Marshall had unsuccessfully sought election to the Virginia General Assembly, although the year of the contest is not given.

[17] Around 1786, Marshall gained public attention by expressing his suspicions about James Wilkinson's negotiations with Spain for free use of the Mississippi River and the possibility of Kentucky's secession from the United States to affiliate with Spanish possessions.

[18] Biographer Anderson Chenault Quisenberry notes, "As to Humphrey Marshall's prominence in the Danville convention, or as to what notable part he acted there, nothing is said by the historians.

[19] The proposed constitution was very unpopular in all parts of Kentucky except Jefferson County, but Marshall openly favored its ratification.

[21] Neither shot injured Marshall, who retaliated by beating Harris with a stick severely enough to force his retreat from the encounter.

[21] Despite his favorable position toward the proposed federal constitution, Marshall was chosen as a delegate to the convention from Fayette County.

[17] On June 25, 1788, he joined Jefferson County delegates Robert Breckinridge and Rice Bullock in voting for ratification.

[24] He opposed allocating men or supplies for George Rogers Clark's proposed attack upon the Spanish at New Orleans.

[3] The attack was promoted by Edmond-Charles Genêt, and Marshall accused sitting governor Isaac Shelby of complicity in the matter.

[3] Partly as a result of Marshall's attacks on prominent Democratic-Republicans such as Governor Shelby, the Federalists gained influence in the state legislature.

[31] Although Marshall was not frequently active in debate on the Senate floor, he was a strong advocate of nearly every Federalist measure considered in that body.

[12] After the expiration of his Senate term in 1801, Marshall returned to his farm and his law practice, seldom acting in the realm of public affairs.

[3] His articles in the newly founded Frankfort Western World newspaper – written under the pseudonym "Observer" – prompted the Kentucky House of Representatives to form a select committee to investigate his charges.

[34] Federal judge Harry Innes, a frequent object of Marshall's suspicions, testified against Sebastian before the committee.

Buoyed by his involvement in the exposure of Benjamin Sebastian, Marshall declared his candidacy for a seat in the Kentucky House in 1807.

[38] Marshall sought reelection in 1808 and defeated his opponent, John M. Scott, by a majority of 11 votes, identical to his margin the previous year.

[40] Clay's chair in the chamber was separated from Marshall's only by that of General Christopher Riffe, the representative from Lincoln County, who was described as "a burly German of almost gigantic size and herculean strength".

[40] A few minor quarrels passed between Marshall and Clay early in the session, but the relative peace dissolved in December 1808 when Clay introduced a resolution calling for all members of the General Assembly to wear "homespun" garments as a means of encouraging local manufacturing and reducing British imports.

[40] Marshall regarded the measure as demagoguery and employed a tailor to make him a suit of British broadcloth to wear on the House floor.

Upon the death of Martin D. Hardin who had been elected to the Kentucky House of Representatives in 1823 but died before he could take office, Marshall pursued an abbreviated campaign for the vacant seat and defeated Jeptha Dudley by a margin of 3 votes.

[48] Harry Innes' libel suit against Joseph Street was not fully adjudicated in the Jessamine County Circuit Court until 1811.