Located five miles south of town on the Post Road lies what remains of old Fort Pena Colorado, built in 1879 to protect area residents from Indian raids.

Around the time that Apache leader Victorio led his band in an escape from the San Carlos, Arizona, Reservation, a military outpost was established next to the prolific spring at Pena Colorado, or Red Bluffs. This not only eliminated access to an important water hole for rebellious Apaches, it also protected the road from Ft. Clark to Ft. Davis, and was easy to support from Fort Stockton, 50 miles to the north. Of even more importance, it lay near the projected route of the Southern Pacific railroad. Abandoned in 1893, some of the foundations of the original structures can still be found.

The town of Marathon grew up around the railroad and what is now referred to as "The Post". Although the army left soon after the defeat of the last wild Apaches, the location remains one of the most delightful habitats in the region. "The Post" is maintained as a county Park and has a spring fed water hole, surrounded by shade trees. This is a favorite place for native and migratory birds of all descriptions, a "must see" location for birders, and a great place for a picnic lunch.