[WhiskeyPapa]

Most if not all of the ships were Northern owned or crewed.

False. Most slave ships were flagged in Britain.

Walt

[AnAmericanMother]

Yeah, and all those ships sailing around now with Liberian registry were built, captained and crewed from Monrovia, right?

[U S Army EOD]

You are wrong again, the English hunted slavers.

[billbears]

False. Most slave ships were flagged in Britain

False

With Great Britain, France, Portugal, Spain, and the United States all having outlawed the Slave Trade by 1820, military efforts were begun by all these nations to enforce the ban

With no way of stopping them, vessels flying the US flag were virtually immune from prosecution, and American ships entered a golden period of slave trading

For the next twenty years, ensuring the ability of US ships to sail unimpeded by others was the main object of the African Squadron

Here

Slavers in the 19th century often found protection for the illicit trade by sailing their vessels under the American flag. This unintended haven was the result of a deep-seated distrust of the fledgling United States toward the British, and their policies in Africa. Since the Revolutionary War and the War of 1812, Great Britain had been the traditional political rival of the US; and as the young nation’s productivity began to grow, also an economic rival.

Here

Of course I'm sure a list of at least some of the ships flying under the union colors and delivering slaves could be produced if need be.