The four-story, red-brick complex with 46 units is meant for residents like Davis - 55 and older, with incomes from $11,088 to $47,520.
The complex was completed last fall, but its developers waited until now to give it the red-carpet treatment, with a ribbon-cutting ceremony Wednesday attended by officials from the city and state, as well as principals of the Altman Group.
Among the speakers was Brett Altman, president of the Altman Group, who praised Johnson for his support, while acknowledging an awkward fact.
"Frankly, we did not support the councilman when he ran for office," Altman said. "But we knocked on his door and asked for help anyway."
And there was no hesitation on Johnson's part.
"I'm still councilman to all the people in my district," he said, shrugging off any suggestion he did anything more than expected under the circumstances. "My job is to represent everyone equally."
It may not have hurt that affordable housing is a hobbyhorse that Johnson has been riding since taking office in 2012. He has made it a mission to assure that low-income residents in his district are not driven out of their neighborhoods by the gentrification that is sweeping through many nearby communities as a result of Center City's boom.
"We want neighborhoods where everyone has the opportunity to raise their families and live in the neighborhood where they were raised," he said.
Affordable housing adds to the stability and diversity of a community, he said.
His commitment to affordable housing has led to skirmishes with a local developer, Ori Feibush, who has promoted pricier, market-rate projects in Johnson's district.
Feibush has said he will challenge Johnson when he comes up for reelection next year. He also has sued Johnson in federal court, alleging that the councilman has illegally blocked his development efforts, a claim Johnson denies.
Although Feibush went unmentioned Wednesday, Johnson made a point of stressing his past support for other market-rate projects while promoting affordable housing as providing a "health balance" to a community.
The subtle politics of the situation were more than likely lost on most of those in attendance. Certainly, Davis seemed simply delighted that she had managed to trade up to a new, bright, airy, $700-a-month apartment - and still stay close to her home turf in Grays Ferry.
"This right here is like a palace compared to where I was," she said. "And I got to stay around my people. I was like the walking dead before. I've come alive. I've been resurrected."