Swim trunks, shorts designed to be worn by men while swimming, came into fashion during the mid-1930s. Trunks replaced much bulkier types of swimwear, which covered the entire torso and was often heavy and hot. Because many men wanted to visit beaches and pools in comfort, and wanted ease and freedom of movement in their swimming clothes, they protested the bulky outfits that had been legally required for swimming.
By the early 1900s men’s bathing suits became more streamlined, but still covered much of the body. In 1916 beaches on Chicago‘s Lake Michigan required men’s bathing costumes to be cut no lower on the chest than the armpits. Bathing suit bottoms had to have a “skirt effect,” or a long shirt had to be worn over the suit. The bottoms themselves could be no more than four inches above the knee. A possible alternative was flannel knee pants with a belt and fly front worn with a vest. Failure to obey these rules could result in arrest for indecent exposure.
Such modest styles began to change during the 1930s. The invention of a rubberized thread called lycra made a new type of snug-fitting bathing suit possible, and a “nude look” came into fashion on beaches everywhere, with tight, one-piece suits that looked glamorous and made swimming easier. However, men still wanted to swim and relax on beaches bare-chested. In 1933 a men’s suit called “the topper” was introduced with a removable tank top that allowed daring men to expose their chests when they wished. That same year the BVD company, which made men’s underwear, introduced a line of men’s swimwear designed by Olympic swimming champion Johnny Weismuller (1904–1984).
In the summer of 1936 a male “no shirt movement” led many men to protest the chest-covering requirements. Although topless men were banned from beaches from Atlantic City, New Jersey, to Galveston, Texas, the men eventually swayed the legislature, and by 1937 it was legal for men to appear in public wearing only swim trunks. Since that time men’s swimwear styles have changed little. Into the twenty-first century swim trunks have been either loose-fitting shorts in a “boxer” style or the tighter fitting “brief” style.