In 1804, Johnson ran for the Kentucky House of Representatives for Scott County (where Great Crossing is) and this time was elected, the first native Kentuckian to serve in the state's legislature. Although the Kentucky Constitution imposed an age requirement of twenty-four for members of the House of Representatives, Johnson was so popular that no one raised questions about his age, and he was allowed to take his seat. Seeking to protect his constituents, most of whom were small farmers, he introduced a proposed U.S. constitutional amendment limiting the power of the federal courts to matters involving the U.S. Constitution. Throughout his political career, Johnson sought to limit the jurisdiction of federal courts, which he deemed undemocratic.