After 1865 they owned them all, both black and white. The Republicans of that era were big government, corrupt, tax and spend liberals. They ushered in an age of "Crony Capitalism" that became known as "The Gilded Age."
They are very akin to modern Democrats, and they resided in exactly the same big cities that modern Democrats still control today.
You’ve overlooked the fact that no Republican owned a single slave.
If one did, you could show me his name.