The San Blas Half Marathon in Coamo, Puerto Rico, is one of the most revered 21-km races in the Caribbean. Since 1963, the Delta Phi Delta fraternity has turned this inland town into a true running festival: thousands of local and international athletes gather to tackle a demanding course filled with hills, fast descents and historic landmarks. The 2026 edition, scheduled for 1 March, once again promises a warm tropical atmosphere where strategy and heat acclimation are just as important as fitness. According to the organizers, the event attracts around 1,000 runners from several countries and more than 150,000 spectators each year, making it a unique cultural experience.
History and significance
The origins of the San Blas race date back to December 1962, when members of the Delta Phi Delta fraternity created a 3-mile race as part of Coamo’s patron saint festivities. Three years later, the distance was extended to a half marathon, and since then the event has welcomed some of the world’s top distance runners. During the 1960s and 1970s, internationally renowned athletes travelled to Puerto Rico to compete. In 1999, Kenyan runner Philip Tarus set a course record of 1:02:10, and athletes from more than 50 countries have participated over the decades. ESPN even featured the race in its “Road Race of the Month” segment, highlighting its international prestige.
Course and points of interest
The certified 21.0975-km course offers a journey through Coamo’s history and topography. More than 14 historic sites line the route. Highlights include:
- Starting line (Calabazas Sector): the race begins at kilometre 36.2 on Route 14, along the road used by Spanish troops during the U.S. invasion of 1898.
- Niágara Sector: runners pass the obelisk honoring fallen soldiers and cross the historic iron bridge built in Belgium in the late 19th century.
- Town center: along Avenida Héroes, participants pass Luis Muñoz Marín Square and admire the San Blas Illescas Church (begun in 1661), as well as the town museum and Baptist church, both dating from the early 1900s.
- Leaving town: the route follows Piel Canela Boulevard past the Osvaldo Rivera Escalera field and the Francisco “Pancho” Coimbre sports complex, then crosses the Manuel Méndez Vigo Bridge over the Las Minas River.
- Ajoguillo Climb: near kilometre 12 lies the famous Ajoguillo hill; tradition holds that the first athlete to crest it often goes on to win the race.
- Road 150 junction and finish: after crossing the Río Chiquito Bridge, runners pass the Delta Phi Delta headquarters and re-enter Coamo along Avenida San Blas; the race finishes in front of the 19th-century City Hall, rebuilt in 1929.
The combination of flat stretches, steep climbs and fast descents requires careful pacing and energy management. Tropical heat and humidity add another layer of difficulty.
Weather conditions and physical demands
Coamo enjoys warm weather year-round. In March, the average temperature is around 23°C (74°F), with highs near 27°C (81°F) and lows around 21°C (69°F), and roughly 100 mm of rainfall during the month. Relative humidity often exceeds 70%, especially in the early morning hours. These conditions, combined with the rolling profile, require runners to plan pacing and hydration carefully.
Registration, categories and prizes
Registration requires completing a form and paying the entry fee. Applications may be sent by post (Fraternidad Delta Phi Delta, PO Box 60, Coamo 00769), and online registration is available through the All Sport Central platform. It is advisable to register early, as entries typically sell out; in previous editions, registration closed about a month before race day.
The race features several divisions:
- International division: open to athletes of any nationality. The top five receive cash prizes of up to US$3,000, with time bonuses for performances under 1:02:10 (men) and 1:11:40 (women).
- National division: reserved for Puerto Rican runners. The top three receive US$1,500, US$1,000 and US$500 respectively.
- Coamo division: for residents of Coamo. The top three earn US$300, US$250 and US$150.
- Wheelchair division: offering the same prize structure as the Coamo division.
- Age groups: categories for ages 18-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59 and 60+; the top three in each group receive medals and cash awards.
In addition, the organization awards medals to the first 1,000 finishers and uses electronic timing to ensure accurate results.
Training and racing tips
The combination of hills, descents and tropical weather makes San Blas a race that demands specific preparation. Consider the following recommendations:
- Hill training: incorporate uphill and downhill repeats to build leg strength and muscular endurance. Long hill workouts will prepare you for the notorious Ajoguillo climb.
- Heat acclimation: schedule some sessions in warm, humid conditions to adapt your body. Maintain proper hydration before, during and after runs.
- Pacing practice: include Fartlek and tempo sessions to handle constant elevation changes. Our guide on Fartlek training explains how to apply speed play effectively.
- Strength and technique: complement your running with strength work for legs and core, plus drills to improve efficiency on climbs and descents.
- Hydration and nutrition strategy: rehearse fluid and electrolyte intake in advance; carry gels or easy-to-digest snacks and consume small amounts every 20–30 minutes during the race.
Travel and tourism in Coamo
Coamo lies in Puerto Rico’s south-central region and is known as “El Verde de las Lomas” (“the green of the hills”). Beyond the race, you can relax in the Baños de Coamo hot springs, explore the central square and historical museum, or hike in the surrounding mountains. Local cuisine features dishes such as mofongo and arroz con gandules, and the beaches of the southern coast are less than an hour away. If you’re travelling from abroad, fly into San Juan and rent a car to explore the island comfortably.
Conclusion and call to action
The 2026 San Blas Half Marathon is more than a race: it’s a sporting celebration that blends history, tradition and physical challenge. If you’re looking for a demanding half marathon in a tropical setting, this is your opportunity. Register early, structure your training and experience the thrill of running through Coamo’s hills and colonial streets. And remember, the SnapRace app can help you plan your workouts, monitor your pace and share your progress with a community of motivated runners. Will we see you on the starting line?