Founded by a presidential decree in 1974, the 68,796-hectare (170,000-acre) Parque Nacional Sierra San Pedro Mártir (7 A.M.–7 P.M. daily, US$7.50 per vehicle) centers around the San Pedro Mártir Plateau (elev. 1,800 m), which covers approximately 70 kilometers by 15 kilometers at the north end of the range.
Given its remote location, it is one of the least visited national parks in all of Mexico, which can make a trip here all the more enjoyable.
Backcountry hikes and self-contained camping are permitted within the park, but infrastructure and services are limited. Few trails are marked, so you’ll need to bring a GPS and topo maps (San Rafael H11B45 and Santa Cruz H11B55), which Santa Barbara, California-based Mexico Maps (U.S. tel. 805/687-1011, www.mexicomaps.com ) sells for US$15.95 per map.
The easiest trails to follow are located along the northeastern edge of the park, near the observatory. If you’re not confident that you can navigate the wilderness environment on your own, you can hire a guide through Meling Ranch (tel. 646/179-4106, www.melingguestranch.com ) or EcoTur (www.mexonline.com/baja/ecotur3.htm ).
Hunting and the possession of firearms (even with a Mexican permit) are prohibited, as is off-road driving. You can build campfires in fire rings at a few sites in the park. As with any wilderness environment, let the local rangers know the details of your trip before you head off on the trail.
Summer temps hover around 26°C during the day, dropping to 4.5°C at night. July and August also bring heavy rains and afternoon thunderstorms to the sierra. In winter temperatures range 4.5°C–12°C, and snowfall is common above 2,000 meters. Days are pleasantly warm in spring and fall, but night can dip below freezing. Accordingly, the best hiking seasons are mid-April–mid-June, when the wildflowers are in bloom and freshwater is plentiful, and late September–early November, before the snows begin.
The park entrance is located 78 kilometers from Mexico 1 via a paved road that heads west from Mexico 1 at San Telmo; follow signs marked Observatorio. Another way to access the Sierra de San Pedro Mártir is via a rough dirt road (high clearance required) through the farming town of Valle de la Trinidad, off Mexico 3 (Km. 121). This route is 48-kilometers long and takes you to the northern boundary of the national park.
Clear air and nonexistent light pollution led the Mexican government to choose Cerro de la Cúpula (elev. 2,830 m) as the location for a world-class observatory, called the Observatorio Astronómico Nacional (Ensenada tel. 646/174-4580, www.astrosen.unam.mx , 11 A.M.–1 P.M. Sat., by reservation).
Built in 1975, its three telescopes (2.1 meters, 1.5 meters, and 84 centimeters) assess the brightness of the sky, the state of the atmosphere, and a long list of meteorological data. This facility is regarded as one of the best places on the planet to observe the stars and planets above. It’s open to the public, but hours are limited and vary by season.
The observatory is located at the end of the park access road, also called the San Telmo de Abajo road (20 km past the park entrance). Park before the locked gate and walk the final two kilometers to the buildings.
Dominican Padre José Loriente established a mountain mission (1794–1824) high in the Sierra San Pedro Mártir to serve a small population of indigenous people, but the rugged terrain and cold winter climate made for a challenging mission environment. Its 20-hectare orchard grew wheat, corn, and beans primarily. Only the faint ruins of a few walls survive today, and access is difficult: from the observatory, it’s a two-day guided horseback ride to reach the site.