What was Thomas Jefferson's contribution to the development of the United States government?

Thomas jefferson was one of america's founding fathers and he wrote the Declaration of Independence.

Jeffersonian democracy, named after its advocate Thomas Jefferson, was one of two dominant political outlooks and movements in the United States from the 1790s to the 1820s. The term was commonly used to refer to the Democratic-Republican Party (formally named the "Republican Party"), which Jefferson founded in opposition to the Federalist Party of Alexander Hamilton. The Jeffersonians were deeply committed to American republicanism, which meant opposition to aristocracy of any form, opposition to corruption, and insistence on virtue, with a priority for the "yeoman farmer", "planters", and the "plain folk".

They were antagonistic to the aristocratic elitism of merchants, bankers, and manufacturers, distrusted factory workers, and were on the watch for supporters of the dreaded British system of government. Jeffersonian democracy persisted as an element of the Democratic Party into the early 20th century, as exemplified by the rise of Jacksonian democracy and the three presidential candidacies of William Jennings Bryan. Its themes continue to echo in the 21st century, particularly among the Libertarianand Republican parties.

At the beginning of the Jeffersonian era, only two states (Vermont and Kentucky) had established universal white male suffrage by abolishing property requirements. By the end of the period, more than half of the states had followed suit, including virtually all of the states in the Old Northwest. States then also moved on to allowing popular votes for presidential elections, canvassing voters in a more modern style. Jefferson's party, known today as the Democratic-Republican Party, was then in full control of the apparatus of government-from the state legislature and city hall to the White House