Ron Daniels, the president of the Institute of the Black World 21st Century, a group that supports reparations, said they would be necessary for America to “fully heal itself.” Any efforts to bring attention to the idea, including a happy hour bearing that name in Portland, could help people organize around the issue, he said.

“Hopefully out of that experience there’s some education that takes place,” Mr. Daniels said.

There was enough interest in the concept to fund occasional happy hours for the rest of the year, though they will be renamed to “Reparations Power Hour” out of concern that the “happy hour” label was unwelcoming to people who do not drink, Mr. Whitten said.

Anticipating some criticism, he noted that it was not meant to diminish the seriousness of reparations. Should anyone question why white people were not invited, he said, “They show up by donating to make sure the event happens.” More than 100 people, not all of them white, donated, he said.

“White people, we have love for you, and we’re going to see you. We can’t not see you,” he said. “Once a month we’re going to have these two special hours that we cannot get anywhere else.”