Ever since 9/11, American Muslims have struggled with whether they should stay under the radar or assert their identity. Despite the discrimination that has risen to the surface since that terrible day, their ranks in the United States have grown substantially, and there are twice as many mosques operating today as there were in 2000. Yet the majority of those new sanctuaries have burrowed into existing buildings — former churches, synagogues, movie theaters, and storefronts.

Because they’re so understated, you might never guess that there are now more than 40 mosques in Philadelphia serving some 200,000 Muslims. Most operate in buildings that don’t include any traditional Islamic architectural features on the outside, apart from a touch of green paint or decorative tile work.

Philadelphia’s Muslims became a bit more visible in October when the Ahmadi sect dedicated a new mosque on a skinny plot of land off Broad Street in North Philadelphia. Its pointed arched windows and modest central dome hint at its purpose. But the 55-foot minaret on Glenwood Avenue confirms it. The slender, buff-colored tower stands tall over the adjacent rowhouse neighborhood, a proud and soaring thing, to use Louis Sullivan’s famous phrase. While another Islamic group, the Bawa Muhaiyaddeen Fellowship, has operated a small, purpose-built mosque on their Overbrook property since 1984, the Ahmadi’s new house of worship is prominently located on a public street. Its minaret, tall enough to be seen for blocks, declares that they have arrived.

Building a statement sanctuary has been a rite of passage for nearly every religious group that has settled here since William Penn welcomed people of all faiths to Philadelphia in the 1680s. Catholics laid the cornerstone for the Cathedral Basilica of SS. Peter and Paul in 1846, when hostility against the religion was at its most fierce. The city’s Jews telegraphed their growing numbers in 1872 by building the Furness-designed Rodeph Shalom on North Broad Street. And two years ago, the Mormons completed a lavish temple compound off Logan Square.

The opening of the Baitul Aafiyat mosque represents a similar milestone for the Ahmadiyya community, an offshoot of mainstream Islam that originated in Southeast Asia. The group has endured a long history of persecution in Pakistan and India, and is still not accepted by many American Muslims, even though its membership is now a melting pot of ethnic groups.

Perhaps because of their diversity, the Philadelphia Ahmadis have been expanding fast. By 2011, the group had outgrown its prayer hall in a porch-fronted house on North 10th Street in Olney and was looking for a place to build a mosque. It found a suitable location in the heart of North Philadelphia, on a trash-strewn lot wedged between Amtrak’s Northeast corridor tracks and the historic boxing gym where Joe Frazier trained. Congregation members considered it a good omen when they realized that the site, once home to a National Biscuit Co. factory, sits at the geographic center of Philadelphia, the chairman of the mosque’s building committee, Abdul Subhan Malik, told me. It’s also halfway between the North Philadelphia and Allegheny stops on the subway.

Since so few new mosques have been built in the region, there was no obvious go-to architect to help with the building. Through word of mouth, the Ahmadis were introduced to Rich Olaya, who contributed to several museums while working for Dagit Saylor. Olaya, who describes himself as a lapsed Catholic, admits he knew nothing about mosque architecture but plunged into the research, visiting mosques in the U.S. and abroad.

He discovered there aren’t many hard-and-fast rules. So long as the building faces east, toward Mecca, “a mosque can be anything, from a circle of stones, to the Great Mosque of Mecca,” explained Ibrahim Hooper, a spokesman for the Council on American-Islamic Relations.

Even so, the Ahmadis wanted to incorporate traditional elements commonly associated with mosques, including domes, Arabic calligraphy, and windows with pointed arches. Since Ahmadis believe in separate-but-equal facilities for men and women, the new mosque also needed two of everything — two entrances, two prayer halls, and a screen dividing the community room.

While the Ahmadis didn’t want the mosque to overwhelm the neighborhood, they were conscious that they were making history. They felt their new building should make a statement, Olaya said. “Just not a grandiose statement.”

His problem was to reconcile all those demands with his own modern sensibility.

In some ways, the project’s low budget proved to be a blessing. Because the congregation’s 400 members were reaching into their pockets to pay for the $8 million building, the design would have to be relatively no-frills.

Olaya kept the two-story building low but stepped it back slightly at either end to suggest wings. Except for domes over the prayer halls and the lobby, the roof is flat. On the exterior, Olaya opted for a buff brick, accented by light brown block, both treated to look like rusticated stone.

Olaya satisfied the Ahmadiyya community’s desire for traditional elements by modeling the minaret on the one built by the sect’s founder in Qadian, India. While the Philadelphia version of the “White Minaret” is only half as tall, it is topped with a similarly bulbous onion dome.

Beyond the slender tower, the brick-trimmed, arched windows form the main decoration on the exterior. Olaya did score one victory for contemporary design: He convinced the congregation to include modern windows on the main facade and building corners, as well as a large bay on the Glenwood Avenue side. Because of their size, the interior is flooded with natural light.

Given the spartan interiors, the gentle light makes a big difference. The only decoration is the painted calligraphy and the thick, Turkish-made carpeting. The bulk of the budget went to functional amenities, including a nursery next to the women’s prayer hall, a library, restaurant-quality kitchen, and several meeting rooms.

The Ahmadis eventually hope to install a basketball court on the large lawn behind the building. For now, they have arranged plants to form the sect’s slogan: “Love for all. Hatred for none.”

It’s not unusual for mosque projects in the U.S. to face local opposition. The Bensalem Masjid, which Olaya is also designing, had to enlist the help of the federal Justice Department after township officials tried to block the project.

That wasn’t the case in Philadelphia. Malik told me that nearby residents cheered when they learned that the Ahmadis were cleaning up the trash-strewn lot next to the rail tracks. One even donated a small strip of land to enlarge the site. The congregation reciprocated by involving residents in planning discussions and has instituted a soup kitchen. Mayor Kenney spoke at the recent dedication.

Modest as the Ahmadiyya mosque is, it represents a major investment for this part of North Philadelphia. The building is alive with activity from morning to night. The pale brick sparkles during the day. At night, the minaret is dramatically lit, offering a glowing beacon to all.

Note: This column was updated to recognize the existence of an earlier, purpose-built mosque, the Bawa Muhaiyaddeen Fellowship, in Overbrook.