In 1913, the US Navy issued its first pullover, buttonless undershirts with elastic collars to sailors and the American t-shirt was born. There's some dispute about the reason. There's the popular story that they were inspired by European soldiers who had cotton undergarments to keep themselves cool under their wool uniforms but our colleagues at Military Times uncovered a story that claims that the Navy issued t-shirts to cover chest hair that was poking out of sailors' V-neck uniforms.
Of course, students of Army history will point out that the t-shirt as a popular outer garment can be traced to troops stationed in the South Pacific during World War II. Although the Army's quarter-sleeve shirts were issued as undershirts, command eventually allowed soldiers to wear them minus the uniform shirts in the heat and humidity. Troops came home, started wearing them when they cut the lawn and worked on their cars in the driveway and eventually someone decided to start decorating them with slogans and logos.
T-shirt printing company CustomInk has launched a tribute site called T-Shirt Birthday. They're currently offering a custom Coast Guard t-shirt as a fundraiser for the Yellow Ribbon Fund, which supports recovering veterans and their families at Walter Reed Medical Center. If you missed out on previous designs for the Navy, Air Force, Army and Marines, all five designs will be available again starting in September.