The minimum wage for nearly half the Washington region would jump 40 to 60 percent over the next three years under a rare effort announced Wednesday by D.C. and Maryland officials to work together to pass similar, if not identical, minimum wage increases by the end of the year.

If the triad of legislative efforts succeeds, it would ensure an hourly salary of $11.50 in the District and Montgomery and Prince George’s counties by 2016.

Lawmakers who unveiled the coordinated plan said it would begin to bridge a growing economic gap in the region, which has the nation’s highest median income, at $88,000, even as nearly one in five District residents live at or below the poverty line and the number of poor residents in suburban counties is on the rise.

By the District coordinating with Montgomery and Prince George’s, D.C. Council Chairman Phil Mendelson (D) said, proponents in all three locales would boost their chances for success.

“This is pretty unusual,” Mendelson said. “We are standing together because so often an issue like minimum wage is argued divisively — that one jurisdiction is going to be at a competitive disadvantage with other jurisdictions. We are standing together to make a clear statement that that’s not going to be the case.”

Regionally, however, the plan also threatened to exacerbate a stark divide along the Potomac River, with lawmakers in Virginia showing no sign of raising the minimum above the federal rate of $7.25 — a wage Congress set six years ago.

“We are just trying to get people closer, so they’re off the floor,” said Montgomery County Council member Marc Elrich (D-At Large), author of the legislation in the largest of the three jurisdictions, whose combined population is 2.5 million. “If we can lift people off the floor, I think that’s really important.”

Lawmakers in Prince George’s and Montgomery — where the minimum wage is $7.25 — introduced legislation last week for an increase. At the time, Mendelson said he planned to throw his weight behind a similar measure.

At a news conference with those lawmakers a few blocks north of the U.S. Capitol on Wednesday, Mendelson said he was in — with a plan to raise the city’s minimum of $8.25 per hour by a dollar in July, by another dollar in 2015 and by $1.25 in 2016.

At that point, the city’s minimum wage would reach $11.50; after that, it would be indexed to inflation.

Prince George’s County Council Chairman Andrea Harrison (D-Springdale) all but assured victory for the plan in her county and suggested lawmakers a few miles south take note of the cooperation.

“We want to show the world that at least some folks can work together here in this region,” Harrison said at the news conference. “The bottom line is that it is expensive to live in this region. Everything has gone up in cost, but the minimum wage has not.”

In Montgomery, the plan put forth by Elrich has only two co-sponsors, but county leaders have lobbied for more than a year for a statewide increase to the minimum wage. In an election year, political watchers say a majority may be compelled to back it.

A similar dynamic is at play in the District. All three council members who have declared candidacies for mayor have supported reviewing the minimum wage. Council member Tommy Wells (D-Ward 6) has proposed an increase to $10.25.

“I do believe we can get our businesses and advocates for justice together and have a new minimum wage that reflects the values of our city,” Wells said Wednesday, a day after holding a news conference of his own at the brewery D.C. Brau, whose owners said they had agreed to raise its wage to $10.25 without a new law.

Mendelson said Wednesday that he has been working with another key voice in the debate in the District — council member Vincent B. Orange (D-At Large), who chairs the committee that will hear five minimum wage bills this month. Mendelson said he thinks Orange will bring to the full council a proposal to reach $11.50. Orange was traveling Wednesday and could not be reached for comment.

In the District, such legislation could immediately affect at least 4,000 workers making minimum wage and eventually help about 43,000 who are estimated to earn less than $12 per hour.

Although Northern Virginia is home to the largest share of the region’s economy, Mendelson and Elrich played down concerns that a higher minimum wage north of the Potomac would drive more businesses south, saying most low-paying jobs are in service industries that could not easily move.

“McDonald’s is not going to pick up and move out of the District or Maryland,” Mendelson said.

There has been growing momentum in Annapolis to raise Maryland’s minimum wage to about $10 an hour. All three Democratic candidates for governor next year have said they will support such legislation when the General Assembly returns in January, and Gov. Martin O’Malley (D) is looking at sponsoring a measure, according to aides.

Similar bills have fallen short in recent years, but the dynamic is likely to be different in Maryland during an election year. The issue is a top priority for labor unions, which remain influential in Democratic primaries.

In Virginia, no legislation for a rate increase has passed in decades. Virginia’s minimum wage law states only that the federal minimum applies in the state.

Bill Turque, Laura Vozzella and John Wagner contributed to this report.