San Blas Half Marathon

The Medio Maraton San Blas de Illescas (San Blas Half Marathon) is one of the oldest and most storied road races in the Caribbean, run every year through the hilly streets of Coamo in the mountainous interior of Puerto Rico. Founded in 1963 by the Delta Phi Delta fraternity as a short 3-mile race, it was extended to the full 21.0975 km half-marathon distance by 1966 and quickly grew into an internationally significant event, drawing runners from more than 50 countries over its history. Its demanding, hilly course and the intense heat of Coamo (one of the hottest towns on the island) have long made it a genuine test, while hundreds of thousands of spectators line the route in a festival atmosphere. The race has attracted a world-class international field for decades, with past champions including Derek Clayton, Henry Rono, and Gaston Roelants; Kenya's Philip Tarus ran a blistering 1:02:10 in 1999. Organized by Marathon San Blas, Inc., the event celebrated its 64th edition on March 1, 2026, with roughly 5,000 registered runners, and remains a bucket-list half marathon for anyone chasing the heritage of Caribbean distance running.