Jantzen began as the Portland Knitting Company, founded in 1910 by Carl Jantzen and John and Roy Zehntbauer. In the first years of the company, they produced mainly heavy wool sweaters, gloves and socks. By 1918 they were making a very popular unisex swimming suit, and the company changed its name to Jantzen Knitting Mills.
In 1920, a logo was added to the swimming suit – a diving girl in a red swimsuit. This became the Jantzen trademark. As styles changed, so did the red diving girl, and the style of her suit can be a hint as to the age of the garment.
In the mid 1920s the Jantzen girl donned her cap and stockings. In the 1930s-40s the figure became more streamlined, her swimsuit became a bit shorter and the stripes are gone from the legs. The Jantzen insignia logo is embroidered on the front of her suit in the 1930’s. In 1948 the logo insignia is gone and the Jantzen diving girl has become a bit more streamlined and her suit becomes strapless.
Through the 1920s and 1930s, Jantzen refined their basic swimsuit into the modern bathing suit. Swimwear continued to be the most important part of their business, but in 1939 they expanded into foundations, and in 1940 they introduced a line of sportswear. During the mid and late 1940s, Louella Ballerino did collections for Jantzen. In 1954, the company again changed its name, this time to Jantzen Inc.
By the mid 1960s, the company developed their sportswear manufacturing. The company went public in 1970, and ten years later was purchased by Blue Bell. Jantzen still produces swimwear and sportswear today as part of Perry Ellis International, Inc.
Written by vintage-voyager.com and glamoursurf.com
See also: Web Foot
See vintage Jantzen from VFG members on Etsy (paid link)

from a 1923 swimsuit
Courtesy of Kristin Wojkowski / Vintage.Swimwear.Collection

from a 1920s swim suit
Courtesy of glamoursurf.com

from a 1920s suit (Notice the cap and stockings)
Courtesy of glamoursurf.com

from a 1920s unisex bathing suit
Courtesy of pinkyagogo

from an early 1930s swim suit
Courtesy of dorotheasvintagecloset.com

from an early 1930s swimsuit (Notice USA embroidered on hat)
Courtesy of pinkyagogo

from a 1930 swimsuit
Courtesy of fuzzylizzie.com

from a mid to late 1930s swimsuit
Courtesy of vintage-vineyard

from a 1930s bathing suit
Courtesy of tintrunk

from a late 1930s swimsuit
Courtesy of cemeterian

from a 1930s/1940s swim suit
Courtesy of glamoursurf.com

from a 1940s swimsuit
Courtesy of glamoursurf.com

from a 1940s reindeer sweater
Courtesy of Ranch Queen Vintage

from a 1940s swimsuit
Courtesy of marie92001

from a 1940s swimsuit
Courtesy of vintage-vineyard

hangtag from a pair of 1940s men’s trunks
Courtesy of fuzzylizzie.com

from a 1940s swimsuit
Courtesy of circavintage

from a pair of 1944 shorts
Courtesy of fuzzylizzie.com

from a 1940s t-shirt
Courtesy of FabGear Vintage

from a 1940s sweater
Courtesy of fuzzylizzie.com

from a 1946 swimsuit
Courtesy of fuzzylizzie.com

from a 1946 sunsuit & skirt
Courtesy of denisebrain

from a 1946 bathing suit
Courtesy of borntoolatevintage

from a late 1940s knit dress
Courtesy of bonton

from a late-1940s/early-1950s pair of shorts
Courtesy of poppysvintageclothing

from late 1940s/early 1950s wedge shoes
Courtesy of thespectrum

from a pair of early-1950s shorts
Courtesy of Inez Underwood Collection

from an early 1950s swimsuit
Courtesy of coutureallurevintage.com

from an early 1950s swimsuit
Courtesy of pinky-a-gogo

from an early 1950s suit
Courtesy of leisa

from a 1950s bathing suit
Courtesy of nostalgic*collection

from a 1950s romper
Courtesy of Ranch Queen Vintage

from a 1950s cardigan
Courtesy of Ranch Queen Vintage

from a 1950s bathing suit
Courtesy of pf1

from a 1950s men’s shirt
Courtesy of pinky-a-gogo

from a 1950s sweater
Courtesy of fast_eddies_retro_rags

from late 1950s shirt
Courtesy of tintrunk

from a late 1950s men’s sweater
Courtesy of fuzzylizzie.com

from a 1950s/1960s strapless suit: shorter logo
Courtesy of glamoursurf.com

from an early 1960s merry widow corsette
Courtesy of pinkyagogo

from an early 1960s sweater
Courtesy of vintagetreasuresgalore

from a 1960s swim suit
Courtesy of coutureallurevintage.com

from a 1960s knit dress
Courtesy of Vanity Flair Vintage

from a 1960s girdle
Courtesy of wyogems

from a 1960s men’s beach cabana set
Courtesy of marie92001

from a 1960s men’s sweater vest
Courtesy of Ranch Queen Vintage

from a late 1960s- early 1970s Hawaiian shirt
Courtesy of Ranch Queen Vintage

from a late 1960s swimsuit
Courtesy of vintage-vineyard

from a late 1960s/early 1970s bathing suit
Courtesy of themerchantsofvintage

from a 1970s pair of men’s trunks
Courtesy of fuzzylizzie.com

from a 1980s cardigan
Courtesy of Ranch Queen Vintage

from a 1980s cardigan
Courtesy of fasteddiesretrorags

from a pair of 1980s men’s swim trunks
Courtesy of Metro Retro Vintage

from a 1980s men’s sweater
Courtesy of Ranch Queen Vintage

from a 1980s polo shirt
Courtesy of Ranch Queen Vintage