Sarah Calhoun had worked years in physically demanding jobs, including five years in the field for the outdoor education nonprofit organization Outward Bound. She once resorted to duct-taping the crotch of her men’s work pants when the seams came apart.

“If they’re not designed to fit a woman’s body, they don’t function properly,” she said.

She approached several companies that made men’s workwear to see if they would create a women’s line, but the response was lukewarm.

In 2004, she shared a table at a local coffee shop with Richard Siberell, a veteran outdoor gear designer. He encouraged her with advice and contacts. Later, he became her mentor and a board member. “He said, ‘Sarah, you’re on to something big here, you need to move on this now,’” Ms. Calhoun recalled.

After spending six months at a company in Bozeman, Mont., sewing backpacks to learn about production, she began making a single pants style she designed herself. She and her roommate at the time were the models. Then she started her women’s workwear company, Red Ants Pants, in 2006, in White Sulphur Springs, Mont.

Now, Red Ants Pants has 10 employees and offers a range of work clothing. Its standard pants cost $139. The company’s revenue is around $500,000 a year, and year-to-date sales are up 65 percent.

Like Ms. Calhoun, Ms. Johnston had no experience with apparel when she decided to start a clothing company. She spent two years learning the art of pattern-making before creating Gamine’s signature product: a pair of dungarees.