The Huffington Post

Over what period of time are we talking about?

Roughly 700 years. The official start is usually given as 1231 A.D., when the pope appoints the first “inquisitors of heretical depravity.” The Spanish Inquisition, which begins under Ferdinand and Isabella, doesn’t end until the 19th century — the last execution was in 1826. At the outset, the main focus was on Jews and “judaizers” — Christian converts of Jewish ancestry who were accused of secretly adhering to Judaism. The Roman Inquisition, created to fight the Reformation, and run from the Vatican, doesn’t come to an end until the 20th century.

—Cullen Murphy: The Top 10 Questions Everyone Has About the Inquisition