Founded by the Spanish in 1579, Coamo was the third city established in Puerto Rico. It dominated the south of the island until the mid-1880s, when political power shifted to Ponce. Coamo town, however, remained an important outpost; several decisive battles were fought here during the Spanish-American War in 1898.
The thermal springs outside Coamo are believed by some to be the Fountain of Youth for which Ponce de León was searching. In the mid-1800s a fashionable resort was built nearby, and people have been coming to soak in the waters ever since. Coamo is also famous for the San Blas Half-Marathon, which brings competitors and spectators from around the world. The race, held in early February, covers 13 miles (18 km) of the city's hilly streets.