I’ve been working on the year 1920, which contains some surprises for me. If you find a fringed “1920s flapper” dress with narrow shoulder straps in a thrift store, it’s probably a costume from the 1960s or later. But evening dresses held up by straps were around in 1920. (More about that in a later post.) The bathing suit pictured (above center) is part of that trend.
While we’re looking at all three suits, notice the different choices for stockings and beach shoes. Each has its own hat, too. First, Butterick 2442:
The label shows that even the editors of Delineator realized that this outfit might not be suitable for use in the water.
This suit is truly sleeveless. The exaggerated hip width reflects the dresses worn that summer.
Strap-top bathing suit No. 2440 also has a lot of fabric in its dress and bloomers, but the shoulders and upper arms are as bare as in a modern swimsuit.
“This being the same cut as the evening bodice does away with the uneven showing of coloring if one tans and wears an evening dress.”
This is a very early 1920s’ reference to a suntan being desirable, and to the bare skin revealed in a strap-top evening dress:
The third bathing suit for women is more conservative (for sizes up to 46″ bust.)
That great hat seems to be included.
Bathing suits for younger girls were also illustrated.
The one on the left resembles adult suit 2240, with straps, bare arms, and a belt that passes through the dress.
I have labeled this “circa” 1920, because the small girl’s suit is No. 1718, indicating that it was first issued in an earlier series. Note how the sleeves and parallel stitching echo women’s conservative bathing suit No. 2445.
Taffeta was a recommended fabric for most of these bathing suits. Don’t forget your parasol  or sunscreen  !
For bathing suits from other years, use the search term “in the swim” in the search box at top right.