In 1872, there were more than 300,000 slaves in Cuba and Puerto Rico. Though the Spanish government had passed a law for gradual abolition in 1870, slaveowners, particularly in Cuba, clung tenaciously to their slaves as unfree labor was at the core of the colonial economies. Nonetheless, people throughout the Spanish empire fought to abolish slavery, including the Antillean and Spanish liberals and republicans who founded the Spanish Abolitionist...