In 1754, upon the creation of Hampshire County, Martin presided as the inaugural justice of the county's court. Under the act establishing the county, the first county court was to have been held in June 1754; however, the first court was not held until December 1757. The first court to be held was, in addition to Martin, composed of justices James Simpson, William Miller, Solomon Hedges, and Nathaniel Kuykendall with Gabriel Jones serving as the Clerk of Court. In 1755, Martin was further appointed as the County Lieutenant of Hampshire County. Martin was then elected alongside Thomas Walker to the House of Burgesses representing Hampshire County from 1768 to 1758. In 1758, Martin and George Washington challenged the incumbents and ran for election to represent Frederick County in the House of Burgesses against Hugh West and Thomas Swearingen. Martin and Washington received considerable support from Lord Fairfax, and the leading Anglican cleric in Frederick County, William Meldrum. Washington received the most votes with 310, followed by Martin with 240 votes, 199 votes for West, and 45 votes for Swearingen. Martin and Washington served alongside one another representing Frederick County until 1761. Martin chose not to run for reelection and retired from legislative politics in 1761.