1940 - Girls could still appear on the beach and be in fashion with a one piece suit. This was the year fro short skating skirts on suits, many dots and flowers. It was also the second year of the war.
1942 - By this time the bra and pants have overtaken the one piece suit in popularity. The bra is shrinking and becoming tighter. In the 1920's wearing such a suit on Long Island would have caused arrest.