The T-shirt evolved from undergarments used in the 19th century, through cutting the one-piece “union suit” underwear into separate top and bottom garments, with the top long enough to tuck under the waistband of the bottoms. T-shirts, with and without buttons, were adopted by miners and stevedores during the late 19th century as a convenient covering for hot environments.
T-shirts, as a slip-on garment without buttons, originally became popular in the United States when they were issued by the U.S. Navy during or following the Spanish American War. These were a crew-necked, short-sleeved, white cotton undershirt to be worn under a uniform. It became common for sailors and Marines in work parties, the early submarines, and tropical climates to remove their uniform “jacket”, wearing (and soiling) only the undershirt.