James Machir and place of birth are not known. In the 1790s he became politically active. From 1793 to 1796 he sat in the House of Representatives from Virginia. He then joined the Federalist Party, founded by Alexander Hamilton. In the congressional elections of 1796, he was elected in the third electoral district of Virginia in the time which meets even in Philadelphia U.S. House of Representatives, where he became the successor of George Jackson on March 4, 1797. Until March 3, 1799, he was able to complete a term in Congress. After the mandate again fell to its predecessor Jackson.
About his professional activities beyond politics there is nothing recorded after leaving the Congress. Between 1811 and 1813, and again from 1818 to 1821 he was again a member of the State Parliament of Virginia. He died on 25 June 1827.