I wrote about the general claim, through the lens of the Nation of Islam's claims in The Secret Relationship, here but it's worth noting that the claims did not originate with the Nation of Islam. The early 20th century German economist Werner Sombart, for example, claimed that Jews were at the forefront of the slave trade, with the Spanish Inquisition and Expulsion leading them throughout Europe, and specifically to become both the first slave traders in America and the first plantation owners. In the end, Sombart's views came from pretty similar sources to The Secret Relationship's- by reading (old) Jewish sources. I explain a bit about how this happened in my above linked post. I'm unclear on whether Sombart is the first to have made these arguments, but they do precede the NOI.