The site was first discovered in 1926, and was photographed from the air in 1930, but the remote site deep in the jungle had little more attention paid to it until Ian Graham spent 10 days here making the first map om 1962. Detailed investigation was begun in 1978 with an archeological project under the direction of Bruce Dahlin and Ray Matheny. To the surprise of archeologists, it was found that a large amount of construction was not contemporary with the large Maya classic cities of the area like Tikal and Uaxactun, but rather from centuries earlier in the Pre-Classic era (see: Mesoamerican chronology. El Mirador flourished from about the 10th century BC, reaching its height from the 3rd century BC to the 2nd century AD, with a peak population of perhaps 80,000 people. The then experienced a hiatus of construction and perhaps abandonment for generations, followed by re-occupation and further construction in the late classic era, and a final abandonment about the end of the 9th century.
The site covers some 10 square miles. There are a number of "triadic" structures, consisting of a large low artificial platform topped with a set of 3 step-pyramids. The most notable such structures are two huge complexes; one is nicknamed "El Tigre", with its tallest pyramid some 180 feet high; the other is called "La Danta", some 230 feet high, making it the tallest Maya structure, including the large platform the pyramid is set upon, an artificially built base covering some 18,000 meters of ground. Most of the structures were originally faced with cut stone which was then decorated with large stucco faces depicting the dieties of Maya mythology.
In the late Pre-Classic at least part of the site was enclosed by a wall which reused some stone from earlier structures.
The site is the center of a series of raised stone pedestrian causeways, one linking it to the site of Nakbé some 15 km away.