The 2.7-mile Bull Pasture and Estes Canyon Trails Loop – which can be extended to 3.7 miles – sits in Organ Pipe Cactus National Monument.
To reach the trailhead, from either Interstate 10 or 19 in Tucson, take Ariz. Hwy. 86 west. You’ll drive for more than 90 miles across the desert and through the Tohomo O’odham Nation Reservation. At the small town of Why, go left/south onto Ariz. Hwy. 85 to the national monument. Upon reaching the Kris Eggle Visitor Center, go right/east onto Ajo Mountain Drive, a one-way that eventually turns to a dirt road. Because of this, expect to drive for 40-50 minutes from the visitor center to the trail. The trailhead is at Mile 11; park in the sand pulloffs.
A small stem to the loop runs northeast from the parking area. Once at the loop, go right/east or counterclockwise and enter the Mount Ajo foothills.
The narrow path heads above a wash, crosses it, then climbs the canyon wall.
At 1 mile in, you can extend hike by going right/southeast up a ridge. In 0.4 miles, you turn right/south and head to a summit called Bull Pasture Viewpoint, so named because ranchers used to pasture their cattle there.
Mount Ajo
From the 3379-foot vista, you have a great view looking southwest into the desert and Mount Ajo to the northeast. Mount Ajo is the highest point in the monument at 4808 feet. The spur to the vista adds 1 mile to the hike.
Back on the main trail, at the spur junction your hike veers northwest and gradually ascends. Along the way, you’ll pass a number of the organ pipe cactus for which the national monument is known.
The organ pipe cactus is so named because it looks like an organ pipe. Those spiny pipes can grow up to 16 feet high. The cactus is exceptionally long-living, reaching maturity after 150 years. The plant grows only in southern Arizona and northern Mexico.
Its funnel-shaped white flowers open at night, when they can be pollinated by bats, and close in the morning. They typically bloom April through June.
Early April through May also is an excellent time to spot wildflowers. Among those you can see, especially after a rainfall, include Mexican gold poppy, desert lupine, purple owl’s clover, reddish-orange globemallow, yellow brittlebush and creosote.
Ridgeline
Atop the ridgeline, the trail passes some interesting rock formations. These formed from erosion as a block of heavy rock making up Mount Ajo rose while the basin below it sank as the land stretched, a common geological process during the past 70 million or so years across the West.
Next, the trail switchbacks down a steep slope into another wash.
At the wash, which is 1.6 miles from the trailhead (2.6 miles if you took the spur to Bull Pasture), you’ve reached the Estes Canyon and are on the Estes Canyon Trail, which crosses the dry run then parallels it.
You’ll loop back to the parking area, which is about a mile away from where you first reached Estes Canyon’s bottom.
The trail at times will be rocky and uneven, so be sure to wear hiking boots and bring a trekking pole. There’s also no shade, so be sure to don sunscreen, sunglasses and sunhat.
TOPO MAP
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