A movement is growing to bring together women across race, creed and political beliefs by luring them off social media and arranging for them to meet in person.

It’s a nice idea, but there’s one catch: The Women’s March on Washington is being organized on Facebook, the nation’s preferred platform to battle over race, gender, politics and just about everything else.

The timing of the event, which organizers began planning the morning after the election but are careful not to call a protest, is aimed at the coming administration of President-elect Donald J. Trump. More than 100,000 people have said on Facebook that they will travel to the capital to participate. The plan is to walk from the Lincoln Memorial to the White House on Jan. 21, 2017, the morning after Mr. Trump’s inauguration.

“We’re doing it his very first day in office because we are making a statement,” one organizer, Breanne Butler, said. “The marginalized groups you attacked during your campaign? We are here and we are watching. And, like, ‘Welcome to the White House.’ ”