In 1774, Juan Bautista de Anza, commander of the Royal Presidio of Tubac, successfully explored a 1200 mile overland route from Sonora, Mexico, into Upper California. This expedition with 240 men, women, and children showed that it was possible to transport livestock, goods, and people overland from Sonora to new settlements in California. The Anza Trail was designated a National Historic Trail by Congress in 1990.

The Visitor Center has been closed since COVID and has not re-opened. However, this is the site of the VERITAS array. Several of the array telescopes are visible to your right just before the Visitor Center.

The VERITAS array, run by the Center for Astrophysics, is a place where scientists use four big telescopes, each 12 meters wide, to study space. We can’t see gamma rays from space because they don’t reach the ground; our atmosphere stops them. But when these gamma rays hit the atmosphere, they make a quick flash of blue light called Cherenkov radiation. The VERITAS telescopes look for this blue light. By studying it, scientists learn about very powerful light sources in space, like huge black holes and other extreme places in the universe.

In the distance, atop of Mt Hopkins you will see a white, vertical rectangular building. This is the MMT, a large telescope built to track astronomical objects along two axis, different from all other telescopes of its era (~1979). The modern, updated version of the MMT is equipped with “adaptive optics”: a flexible secondary mirror which creates extremely sharp astronomical images by correcting for distortions created by Earth’s atmosphere.

The MMT has been used study gravitational waves, observe exoplanets, analyze star-forming regions, and study supermassive black holes.

Mount Wrightson (O’odham: Ce:wi Duag) is the highest peak in the Santa Rita Mountains (a 9,456-feet). Infamously, Mt Wrightson is known for the Boy Scout tragedy of 1958. On November 15th, six scouts aged 11 to 16 were hiking the mountain when caught out in a snowstorm. 3 of them died. From this tragedy, the Southern Arizona Rescue Association was formed.

“Baboquivari Peak is an important regional geographic landmark and one of the most sacred sites for the Tohono O’odham (“Desert People”) of Southern Arizona and Northern Sonora. According to the traditional religion of the O’odham, humanity emerged into the world through this holy mountain after a flood. I’itoi, the creator of the world, is believed to live in a cave within the mountain from which he watches over his people today. The image of I’itoi – depicted in Tohono O’odham art as a man in the middle of a circular maze – is popular throughout the Arizona-Sonora border region. The maze represents not only the path to reach I’itoi within his cave at Baboquivari but also the decisions a person makes throughout their life path.” [Nomadic Border]

At mile 21, you get a big, explosive view of Devil’s Cash Box. A mountain with 4 distinct peaks and a geology distinct from any other mountain or hillside nearby.

~ 240 to 330 million years ago sedimentary rock was laid on the ocean floor and was later thrust to the surface by movement within the earth. The Devil’s Cash Box mountains were formed of hard sedimentary rocks like siltstone and limestone. Nearby, the softer sedimentary rock of sandstone eroded (faster) into low round hills. And to the east, the igneous, volcanic rock of the Santa Rita mountains stands tall, largely unphased by erosion. [On-site kiosk at Astronomy Vista]

The Sierrita Mine (or sometimes known as the Duval mine) is a large copper mine located in the Sierrita Mountains of Arizona, with one of the largest copper reserves in the world. First mining claims were recorded in 1895. It was first worked as an underground mine beginning in 1907; and open-pit development began in 1957. Today the mine is owned by Freeport-McMoRan. It is estimated that in 2022 the mine had an economic impact of $463 in the state of Arizona and was responsible for 4300 jobs. (Click on image.)