Maryland’s Aberdeen Proving Ground opened in 1917 and today is the military’s oldest weapons-testing facility in the United States. It’s a big operation. At its peak in World War II, Aberdeen had housing for more than 27,000, and today it still employs more then 12,000 people.

Through its first decades Aberdeen was a man’s world. But that changed during World War II. LIFE covered extensively the real-life Rosie the Riveters who moved into industrial jobs during that era, and the women who became weapons-testers for the first time in Aberdeen were part of that same phenomenon.

The story in LIFE’s Feb. 1, 1943 issue described how the soldiers who once worked the testing grounds but had been deployed overseas were at first replaced by male civilians. Then “as the draft hit hard, the civilians began to disappear and in their place came thousands of women.”

And who were these women?

The women come from everywhere. Many have husbands in the Army. Others have husbands who also work at Aberdeen. They wear bright-colored slacks, and their “firing fronts” are a rippling blend of pink. blue and orange, mixed with white and black powder from the guns. They serve on crews of all weapons up to the 90-mm A.A.’s. [anti-aircraft guns]. They handle highly technical instruments. They drive trucks, act as bicycle messengers, swab and clean vehicles. A few of them have even been tested as tank drivers, but that work, with its physical bruises, is still a little too tough for them.

The declaration of that last sentence reflected a time when women were making their first inroads to military service. In 1942 the WACs had just come into being (see LIFE’s coverage of the first WACs here) and the change in attitudes about what roles women could play was slow and incremental. It was not until 2015 that the Department of Defense opened all military occupations and positions to women.

The photographs by Myron Davis and Bernard Hoffman capture a world in transition. Some pictures indulge in the novelty of the moment—such as the photo of a woman who looks like a schoolmarm set up behind the sites of a machine gun with an ammunition belt being fed through it. But in other photos the women, such as Mrs. Ruby Barnett, a grandmother who had never fired a gun before coming to work at Aberdeen, look right at home in their new jobs. Those pictures seem to ask the question about the women taking on this new line of work: Well, why not?

A woman tested a 30 caliber machine gun at the Aberdeen Proving Ground in Maryland, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

Women loaded shells into an anti-aircraft gun at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

A group of men and women tested a 90 mm anti-aircraft gun at the Aberdeen Proving Grounds in Maryland, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

Viola Testerman carried a 41-pound shell at the Aberdeen Proving Ground, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

Betty Wainwright and Opal Burchette fed cartridges into magazines at the Aberdeen Proving Ground in Maryland, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

Nealie Bare at work at the Aberdeen Proving Ground in Maryland, 1942. Here she hammered a plug into a test shell to keep the shell’s sand from running out.

Bernard Hoffman/Life Picture Collection/Shutterstock

Mrs. Ruby Barnett, a grandmother, had never fired a gun before coming to work at the Aberdeen Proving Ground in Maryland during World War II.

Bernard Hoffman/Life Picture Collection/Shutterstock

Mrs. Ruby Barnett at work at the Aberdeen Proving Ground, Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

Mrs. Ruby Barnett was among the women who tested artillery at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

Mrs. Ruby Barnett, a grandmother, tested a carbine at the Aberdeen Proving Ground in Maryland, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

Women fired machine guns at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

Women tested machine guns at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

A woman loaded a bullet aircraft cannon at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

A women tested a 20 millimeter aircraft cannon at the Aberdeen Proving Ground in Maryland, 1942.

Myron Davis/Life Picture Collection/Shutterstock

Aerial view of testing range at Aberdeen Proving Ground in Maryland, 1942.

Bernard Hoffman/Life Picture Collection/Shutterstock

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