James Young is just old enough to remember the era that seared his small Mississippi town of Philadelphia on to the national consciousness.

The infamous murders of three civil rights activists in 1964 laid bare the bitter racism and official complicity in the lawlessness underpinning segregation in the south, and years later prompted the film Mississippi Burning.

But the racists soon lost the struggle to prevent Philadelphia's black residents from voting and this week it resulted in exactly what old Mississippi had tried to prevent – the election of Young as the town's first African-American mayor with white votes helping deliver him victory.

"Philadelphia has some of the worst history and now some of the best. This is a reversal of some of the views that have been dominant in the community," Young said today. "There was a time when this could not have happened. Now it is accepted by everyone. There's not a major riot in the streets because I'm black."

The 53 year-old Pentecostal minister's victory was perhaps more evolution than revolution in the town of 7,300 people, about 40% of them black. African Americans have been filling elected positions in Philadelphia and the state for years with white support, including Young who served on the local legislature. The old racists who controlled the council and police, and won popular support by opposing civil rights, are dying off and their successors are marginalised.

Still, Young's election has an important symbolism in a town that came to represent all that was wrong with the old south.

"It will erase the thought that we're just a southern racist town," Dorothy Webb, 72, a white retired school principal told the local newspaper.

The 1964 murders of the three civil rights workers – an African-American man from Mississippi and two white New Yorkers, all in their twenties - shocked the country not only because of the crime but because of the complicity of local officials in the killing and cover up.

As the FBI hunted for the missing activists, the local sheriff, Lawrence Rainey, said they had gone into hiding to embarrass Mississippi. The state governor, Paul Johnson, suggested they were in Cuba.

During the search, the FBI discovered the bodies of seven other black people who had been murdered in and around Philadelphia without inquiry by the local police. Even after the civil rights workers corpses were found six weeks after they were shot, justice was slow in coming. Mississippi officials declined to prosecute. Seven people, including a police deputy and a Ku Klux Klan leader eventually convicted on federal civil rights charges, served only light sentences.

Mississippi took action for the first time only in 2005 when Edgar Ray "Preacher" Killen, a KKK organiser who is now 84, was convicted of the three murders and sentenced to 60 years in prison.

For years Philadelphia lived with the legacy of the killings. Ronald Reagan chose the town to launch his 1980 presidential campaign with a speech about states' rights, taken as a stand with southern whites opposed to federal civil rights laws.

But however Philadelphia was still seen, it was also changing as Young's own progress showed. He trained as a paramedic and rose to head the county ambulance service for 20 years. He was also elected to the local legislature four times and served on the planning board for 12 years.

That helped make him a safe choice in the election.

"A lot of barriers I would normally have had to overcome were overcome because of my work in the community," he said.

Still, Young doubts he could have won before.

"Ten years ago I think I would have had a good showing but I wouldn't have won. But changes in our nation and the age of people make it more acceptable. We're getting more diverse younger citizens," he said.

By Young's count he picked up about 30% of the white vote and won with only a 46% vote margin out of the 2,000 cast. That may not be a clear endorsement but it still represents a significant shift from the past because, while most whites did not vote for Young, he says they will accept him as the legitimate mayor of Philadelphia when he takes office in July.

Young was also helped by a few factors beyond his control. His opponent, the incumbent mayor, Rayburn Waddell, is elderly and after 12 years in office was widely regarded as having run out of steam.

Then there was Barack Obama.

"Obama's election sent a message to our people that it was possible. If we can elect a black man as president we can elect a black man as mayor of Philadelphia. In the last couple of weeks I was hearing that a lot in the community," he said.

Young's wife, Sheryl, said it is all a further reminder that the old Mississippi is dying.

"Most of the people who were so mean and hateful are dead. They're gone. Whether they instilled something in their children we don't know and we don't care," she said. "Things have changed from being openly hateful. It's a new day. Let's move on. We're not going to forget it. But do I harbour it? No. We have to move on."