Mary Hynes, the outgoing chair of the Arlington County Board, challenged residents and businesses Wednesday to step up their involvement in local public affairs, calling the near future “a moment . . . maybe comparable to what happened after Sept. 11.”

Hynes, giving the 2015 State of the County address to the local Chamber of Commerce, said the small but wealthy county is not likely to see the burst of growth that it experienced in the late 1990s and early 2000s, but what happens next will set the stage for Arlington’s future.

“We have the opportunity once again to be on the leading edge of what the second generation of smart growth is,” she said. “The whole community has a responsibility to engage. . . . This is a moment [which] will be comparable to what happened after Sept. 11 in terms of being a fundamental questioning of ourselves. . . . This is a moment when we start to chart a new course. So I challenge each of you to be part of the solution. Ask yourselves what are you willing to do personally to make this transition as smooth, as strong, as committed to the future as it possibly can be.”

Hynes, who will not run for reelection in the fall, has been on the County Board since 2007 and previously served on the School Board for 12 years. She has often paid tribute to the boards of the 1970s, which made fundamental decisions about putting Metrorail underground beneath then-struggling commercial corridors. The county’s nationally recognized leadership in smart growth planning and execution stem from those decisions.

The hardest decision she had in 20 years in public office, Hynes said, was her vote in November to discontinue the Columbia Pike streetcar project.

Mary Hynes, the outgoing chair of the Arlington County Board, in a file photo from 2011. (Mary H. Hynes)

“I really didn’t believe there was enough bandwidth to address these other pressing needs. Everything was being evaluated through the streetcar lens,” Hynes said, adding that she didn’t have “a whisper of doubt” that buses will prove to be insufficient along the Pike if development proceeds as the county expects. “But our community wasn’t there, our community didn’t understand it, and it was just coloring the conversation to an extent where we couldn’t move forward.”

Even though the Metro and transit corridors have not been built out, Arlington is struggling with a countywide commercial vacancy rate of 21 percent, overcrowded schools and a transportation network that is in some cases overused. The boom may be over, but the county has continued to make long-term investments in infrastructure, adding parks, schools and road improvements, she said. The County Board and School Board, which have had difficult relations in the past, are now working together more smoothly, she said.

This fiscal year, Hynes added, the County Board has closed 27 deals that will bring 5,000 jobs and fill more than a million square feet of office space, representing almost $250 million in investments. A county transit plan will be presented in July, a three-year-long affordable housing study is almost complete, and a community facilities study and a retail action plan are underway, she said.