From Day 1, the mission of Theater of the Seventh Sister has been to produce works that promote evolution and progress in the local community.

Now the nonprofit theater has a found a building in which to pursue and expand that mission well into the future.

Seventh Sister has signed a lease-purchase agreement to eventually buy the former Stahr Armory at 438 N. Queen St. Until recently, the theater had shared space there with the Pennsylvania National Guard, which has since moved.

In an ambitious undertaking, Seventh Sister plans to turn the 36,000-square-foot structure into an arts and sustainability center, housing a range of artistic and eco-friendly organizations.

"We're trying to create a really new concept," said Seventh Sister's co-artistic director, Gary Smith.

Founded in 1989, Theater of the Seventh Sister began using Stahr Armory for its performances in 2007.

At the time, "it was a functioning Army base," Smith said. In fact, there's still a pistol range in the basement.

Headquartered at the armory was the 328th Brigade Support Battalion, a medical unit. Late last year, the Guard relocated to a new readiness center and field maintenance facility in Mount Joy Township.

The state owns the armory, Smith said, and is asking for $871,000. The lease-purchase is for three years, and Seventh Sister pays a monthly rent which goes toward that purchase, he said.

The theater is forming a capital campaign to raise money to buy the building and cover renovation costs, Smith said. The hope is that enough funds are generated so the theater doesn't have to incur a mortgage, he said.

The two-story back of the red-brick building dates from 1916, while the three-story front was erected in the 1930s.

Smith said he loves how the structure possesses architectural character (such as high ceilings) while being "very utilitarian."

And at $871,000, "it's a real bargain for a building that size," he said.

The theater wants to convert the armory into a true "green" facility, with features like solar roof panels. Seventh Sister also plans such upgrades as renovating the restrooms; adding more-efficient lighting; installing a cooling system; and improving handicapped access.

The building's utility costs have already been cut in half, Smith said.

Though it's been around for more than two decades, the theater has never been in a hurry to find a permanent home, he said.

Too many nonprofits think acquiring a building will solve all their problems, Smith said. But Theater of the Seventh Sister has been careful to avoid that "edifice complex," he said.

"We're really conscious of protecting our mission," Smith said.

The key is finding the right building, he said, and Stahr Armory fits the bill.

The structure, which Seventh Sister is tentatively calling Stahr Center, will house two theaters along with more than two dozen offices/studios, conference rooms and rehearsal areas.

Marie Winger, president of the theater's board of trustees, said one advantage of the layout is that the performance spaces can be reconfigured "anyway you want."

It's also convenient that the building is next to a planned city parking garage, Smith said.

Stahr Center will be an incubator of small arts and sustainability organizations committed "to the positive evolution of Lancaster city," he said.

Buy Fresh Buy Local and the Susquehanna Sustainable Business Network are two examples, Smith said.

He said he envisions Stahr Center as a "functioning village" where everyone sustains and supports each other.

Winger said these organizations won't have a typical tenant-landlord relationship with Seventh Sister. Instead, they'll have potential to buy in, she said.

Smith said Stahr Center could even serve as a new business model for nonprofits.

"I think we're doing some real groundbreaking stuff."