Cardinal (Catholicism)
While the number of cardinals was small from the times of the Roman Empire to the Renaissance, and frequently smaller than the number of recognized churches entitled to a cardinal priest, in the 16th century the College expanded markedly. In 1587, Pope Sixtus V sought to arrest this growth by fixing the maximum size of the College at 70, including 50 cardinal priests, about twice the historical number. This limit was respected until 1958, and the list of titular churches modified only on rare occasions, generally when a building fell into disrepair. When Pope John XXIII abolished the limit, he began to add new churches to the list, which Popes Paul VI and John Paul II continued to do. Today there are close to 150 titular churches, out of over 300 churches in Rome.

Q: Who removed the cap on cardinals in the College of the Cardinals?
Pope John XXIII