After nearly 30 years on the Portland City Council, Cheryl Leeman announced Tuesday that she will not seek re-election this fall, so that she can spend more time with her family.

Leeman’s tenure on the council is particularly noteworthy because she has been a conservative voice for so long in what is often described as Maine’s most liberal city. Her term expires at the end of this year.

“I am grateful to family, friends, neighbors and city staff for their support over the years, and it has been a privilege to serve this great city,” Leeman said in a written statement. “Portland is a different place than it was in the ’80s when I was first elected, and I am ever so proud to have been a part of its evolution to a nationally recognized place to live, work and raise your family.”

Leeman, who was a longtime regional representative for now-retired Republican U.S. Sen. Olympia Snowe, has represented District 4, which includes parts of Washington Avenue and the northeastern section of the city.

In 2007, Leeman was diagnosed with breast cancer. She underwent a double mastectomy. When she returned to work a month later, she used her experience to promote the importance of regular cancer screenings.

The registered Republican has long been a voice on the council for conservative spending.

“She was always very interested in the impact of programs and services on the taxpayer,” said former City Manager Joe Gray. “She understood Portland had residents of varying incomes and means.”

Leeman also has been a strong advocate for business, most recently opposing a 5-cent fee on disposable shopping bags and a ban on polystyrene containers, and voting in support of a liquor license for Sangillo’s Tavern, which police have called a trouble spot and targeted for closure.

In Leeman’s time on the council, the Old Port and the Congress Street corridor have been transformed into tourist attractions that are fodder for national lists.

And the city’s politics have become more liberal, especially in recent years. The council now has two members who are in the Green Independent Party, for example, and voters last year made Portland the first city on the East Coast to approve a ballot initiative legalizing marijuana use for adults.

Leeman said in an interview that when she first ran for City Council, in 1984, it was truly a nonpartisan position. “It’s only over the last few years that it’s become very partisan,” she said.

Mayor Michael Brennan said the council will miss Leeman’s perspective.

“We will certainly miss her historical and institutional memory on the council,” he said. “She clearly has been a strong advocate for her district and the city as a whole.”

Leeman’s popularity in District 4 was clear in recent elections. She ran unopposed in three of the past five elections, according to the city clerk’s office. In contested elections, she won 71 percent of the vote in 2011, 58 percent in 2005 and 76 percent in 1996.

Leeman opposed the creation of Portland’s new position for a popularly elected mayor, arguing against paying a full-time salary to someone who doesn’t have much authority.

Brennan, the first mayor to fill the position, removed Leeman from the coveted Housing and Community Development Committee in 2012, appointing her instead to the Nominations Committee. Leeman, along with City Councilor Jill Duson, has clashed with Brennan over councilors’ right to access the council agenda to address constituents’ concerns.

Leeman said she plans to remain active in the East Deering Neighborhood Association, which she helped found. Asked if she is considering running for mayor next year, she replied, “I’m keeping all of my options open.”

Over three decades, one of the most challenging experiences was her second term as mayor, in 2001, after longtime City Manager Bob Ganley died of a heart attack. Leeman oversaw the day-to-day affairs at City Hall, presiding over remembrances for Ganley and guiding the transition to a new manager.

“She stepped up and provided good leadership for the city in a very troubled time,” said Nathan Smith, a former mayor and councilor.

Gray, who replaced Ganley, said Leeman helped him settle into his new position by helping to prioritize issues, build relationships with councilors and draft his first municipal budget.

Later that year, she helped the city cope with the Sept. 11 terrorist attacks. Two of the hijackers flew through the Portland International Jetport, a still-unexplained link to the attacks that put the city on edge.

At the same time, the city was embroiled in a debate about the future of its working waterfront, so Leeman established a 32-member committee to create a new master plan for the eastern waterfront.

Tom Valleau, who was the city’s waterfront director from 1980 to 1998, said Leeman was mayor when the city welcomed its first cruise ship, in 1989.

“The ship was called the Bermuda Star, and by today’s standards it was a rust bucket, but we were thrilled,” Valleau said.

This year, Portland expects 74 cruise ships, carrying 82,000 passengers.

Valleau was disappointed to hear that Leeman will not run for re-election, saying, “It’s going to be a big loss to the civic scene.”

Leeman, who was elected to a three-year term on the school board in 1981 before joining the council, said her ability to help her constituents kept her motivated and gave her the greatest sense of accomplishment.

She recalls helping an elderly woman, who was confined to her home, get the city to replace a tree that had been destroyed by a snow plow, so she could watch and listen to the birds in the tree.

“It doesn’t sound like a big deal, but for her it was huge,” Leeman said.

In recent years, Leeman pushed to have a stormwater project near Mona Road completed. The project ended up saving residents money in insurance premiums by removing the neighborhood from the Federal Emergency Management Agency’s flood maps.

“It’s those personal stories that are the best ones,” she said.

Leeman’s announcement immediately stirred interest in the District 4 council seat.

Two-term school board member Justin Costa announced his candidacy. More potential candidates will likely surface once nomination papers become available on June 30.