In 2007, Mr. Obama came for a fund-raiser when he was running for president. He called the island “one of those magical places where people of all different walks of life come together, where they take each other at face value.”

According to the book “African-Americans on Martha’s Vineyard,” a 1947 article in Ebony magazine said the “most exclusive Negro summer colony in the country is at quaint historical Oak Bluffs on Martha’s Vineyard.” It added, “Negro and white swim together on the public beaches, rub shoulders at public affairs.”

Forty-two years later, in 1989, Ebony again declared the island “a vacation mecca.”

The heritage trail includes stops at the houses of former Senator Edward Brooke of Massachusetts, the first black senator after Reconstruction and the first from the North; former Representative Adam Clayton Powell Jr.; and Dorothy West, a Harlem Renaissance writer who for two summers in the 1990s was visited by Jacqueline Kennedy Onassis, another Vineyard resident and a Doubleday editor who guided Ms. West to finish her novel “The Wedding.”

Also on the tour is the oceanfront mansion of Joseph Overton, the onetime Harlem labor leader, which was known as the Summer White House of the civil rights movement. It faces the Inkwell beach, named long ago by black youths or black writers  no one seems certain. The house’s visitors included the Rev. Dr. Martin Luther King Jr., who vacationed on the island with his family a number of times, as well as Joe Louis, Harry Belafonte and Jesse Jackson.

The exclusive Chilmark area has Rebecca’s Field, land that the enslaved Rebecca Amos inherited and farmed until 1801. Edgartown has a plaque honoring the daughter who was taken from her to be enslaved elsewhere, Nancy Michael, called “Black Nance.” It calls her “a most singular character”  in the words of an 1857 obituary  for the spells she conjured for departing ship captains.

And on Chappaquiddick is the dilapidated house of her grandson, William Martin, who became one of the few black whaling ship captains in New England.

The tour guide, Alex Palmer, said the heritage trail group had been trying to raise money to restore the 1830 house or see it sold to someone who would do the restoration, but had been unsuccessful. Yet when he drove to the site, a new owner, Michael Partenio, was there with his two young sons.