In 1841, Andrews hatched a plan to make his political and moral beliefs a lived reality: He would convince Great Britain to buy up all the land in Texas on the condition that they free Texas’s slaves. The idea was not as outlandish as it might sound. In 1833, Great Britain had done something similar in abolishing slavery on its plantations in the West Indies. There, slaveholders were paid a total of $20 million sterling in recompense for their lost property, though they retained the land. And Texas had already reached across the Atlantic for economic aid. The South Carolina...