It was 1940 and the second year of the war. A girl could still appear on the beach and be in fashion with a one-piece suit. This was the year for short skating skirts on suits, many dots and flowers.
By 1942, the bra and pants had overtaken the one-piece suit in popularity. The bra is shrinking and becoming tighter. In the 1920s, wearing such a suit on Long Island would have caused arrest.
The Jantzen suit in 1945 made for mass sale is comparatively conservative. It has a fair-sized bra, and skirt that covers the pants.By now almost all US beaches have given up trying to regulate bathing suits.