When Randall Woodfin became mayor of Birmingham, Ala., last year, the city once known as the “Pittsburgh of the South” had long been transformed. At one time a manufacturing hub where smoke billowed from the furnaces of steel mills, Birmingham's economy now centers around finance and health care.

But that boom isn't benefiting everyone, particularly not the 77 percent of residents who are African-American.

“Many of our black residents aren’t finding jobs in our new industries,” says the 37-year-old Woodfin, who is black.

To help address that, Woodfin is stepping up investment in workforce training and hoping black residents can leverage that into new jobs.

There was a time when African-American mayors enacted policies aimed explicitly at helping black residents -- demanding, for example, that local companies hire black workers. Atlanta Mayor Maynard Jackson, who led the city from 1974 to 1982, threatened to withhold funding to expand the Atlanta airport if black contractors weren't adequately represented. Similarly, Detroit Mayor Coleman Young moved swiftly to integrate the city's police department, hiring its first black police chief and openly taking race and ethnicity into account when hiring new officers. (The percentage of black officers rose from 10 percent to 50 percent during his 20-year tenure in office.)

Those days seem to be gone.

African-American mayors today are more likely to pursue a policy agenda with broad appeal to all their constituents. Part of the reason for that shift -- at least when it comes to demanding that a certain percentage of city contracts go to black-owned businesses -- stems from a 1989 Supreme Court ruling that deemed it unconstitutional to use city contracts as a lever for black economic gains. But it's also because of demographic changes that have eroded black voter bases in big cities like New York, Los Angeles and Chicago -- places that elected black mayors in the past but haven't had one since the late 1980s.

Chicago, for instance, once had the nation’s second-largest black population, but the city has lost nearly a third of a million black residents since 1980, shortly before electing its first black mayor, Harold Washington. Meanwhile in Atlanta, once the standard-bearer for black municipal power, Mary Norwood last year nearly became the city's first white mayor in more than 40 years, losing by just 821 votes to Keisha Lance Bottoms. Whites made up one-third of the city’s population in 2000; today they account for 40 percent.

Nationwide, as black residents have moved out of cities, and as more white residents have moved in, the prevalence of black mayors has waned. In 2000, there were 19 black mayors in the 50 largest American cities. Today, there are seven. This week though, Supervisor London Breed became San Francisco's first black female mayor.

“Part of the challenge is many African-Americans have left the Northeast and Midwest, places where black populations were once substantial, and where black politicians once held significant power,” says Michael Leo Owens, an Emory University political scientist.

Even in cities that still have a majority-black population, most black mayors today must build and hold onto multi-racial voting blocs to stay in power.

In Atlanta, where black voters no longer have a lock on electoral politics, it was the city's affluent white east side that was pivotal in Keisha Lance Bottoms' victory. In Washington, D.C.'s 2014 mayoral race, majority-white precincts in a city with a burgeoning white electorate broke hard for the runner-up David A. Catania. Muriel Bowser won by holding on the city's majority black precincts and winning precincts that were racially mixed. 

Balancing the need to appeal to a broad voter base and the need to keep the black vote isn't easy, Owens says.

“[Black] mayors are still struggling with the grand challenge that has always been a challenge," he says, "which is to maintain a coalition to achieve progressive policies that are beneficial to black people.”

One case in point: The recent, controversial push in many Southern cities to remove statues honoring Confederate soldiers. Different African-American leaders have responded in different ways.

In Baltimore, Mayor Catherine Pugh last August decided to remove four Confederate statues in the middle of the night without warning. In Richmond, Va., Mayor Levar Stoney, who has said he supports removing the statues from their prominent position along the city's Memorial Avenue, last year convened a commission to study the issue further. The commission's report was recently pushed back until July.

Meanwhile, in New Orleans, where former Mayor Mitch Landrieu (who is white) last year made national news by removing four Confederate memorials from public spaces, the decision of what to actually do with those statues has now fallen to Mayor Latoya Cantrell, who took office last month. Cantrell, who is black, has been criticized for choosing to involve a small group of Confederate monument supporters in that decision-making process.

Every mayor must confront those sorts of balancing acts, but the challenge can be more acute for black leaders.

“The mayor in Richmond has more challenges than the mayor has in Baltimore,” Owens says, pointing to Baltimore’s larger black voting base.

Baltimore is 63 percent black, while Richmond has a razor-thin black majority. And according to recent polling, the majority of residents in the greater Richmond area prefer to leave the statues up.

“But some of this comes down to gut checks,” Owens adds, “whether Stoney is just going to remove the monuments and deal with the consequences. He may not be ready to go to the mat.”

While the number of African-American mayors in big cities has declined, they're not on the decline everywhere. Black mayors -- along with black populations -- have remained somewhat strong in medium-sized cities like Birmingham, New Haven, Conn.; and Flint, Mich. And last November, seven cities, including St. Paul, Minn., and Helena, Mont., elected their first black mayor.