SH 42 was originally proposed on April 22, 1919, as a route from Greenville to Marshall.

[2] On August 21, 1923, the northwest terminus extended north to Sherman, replacing a section of SH 11.

[8] On March 19, 1930, the route was rerouted over the spur back to Mineola, while the section from Gilmer to Marshall was renumbered SH 155, but the section from Greenville to Whitewright was erroneously omitted from the state highway log, and the highway from Alba to Quitman was erroneously omitted from the state highway log, so had no number.

[9] On November 30, 1932, the section from Whitewright to Greenville was added back to the state highway log, and the road from Alba to Quitman was added to the state highway log as SH 182.

[10] On September 26, 1939, the entire remaining route was already part of U.S. Highway 69, so SH 42 was cancelled.