National Review's Mark Krikorian — who, believe it or not, is executive director of the Center for Immigration Studies — drops in this little gem at the Corner:

During slavery and Jim Crow, a number of blacks moved abroad, to Europe or Africa or the USSR, but again, these movements never gained much traction….

Actually, I think very few slaves got the opportunity to move abroad — like, about zero.  Because there were, you know, slaves.

And Liberia?  Yeah, that was an African colony formed by ex-slaves, with the encouragement of whites, although typically free blacks didn't elect on their own voliation to emigrate there; rather, the one-way ticket to Liberia was offered to them in exchange for freedom from the bonds of slavery.

But there really really wasn't a significant number of black who moved to Europe during slavery or Jim Crow.  There just wasn't.

Pictured below: A black family contemplates their upcoming move to Paris, hoping to trade their forty acres and a mule for frequent flyer miles

UPDATE:  National Review's Mark Krikorian responds in the comments below, providing cites.

From what I gather, Krikorian's assertion that there was black emigration during slavery and Jim Crow eras rests upon the fact that some blacks, after serving in Europe during WWI, decided to stay there, mainly in Paris.  The actual number of black emigres amounted to "several hundred", out of over 200,000 black Americans who served in the Army (according to Krikorian's sources).

Oh, and then there was a handful of prominent black artists — like James Baldwin and Josephine Baker – who found havens in various European cities.

Still, to suggest that these rare examples represent a "movement" that "never gained traction" certainly overstates the factual truth.  Rank-and-file African-Americans — those without benefit of military service or fame — certainly were not in a financial position to move abroad during the eras of Jim Crow and slavery.  Especially slavery.