This route is the most direct but by no means the only option. Please see the map for other loop ideas.
See the main page.
From the uppermost parking area, find the Old Baldy trailhead at a sign. Walk up the initial segment, which is an old road. After 0.3 mile, the Old Baldy Trail veers hard left to Josephine Saddle. Stay straight, now on the Vault Mine Trail (also signed as the “Very Steep Trail”). Walk another 0.5 mile to another sign. The Vault Mine Trail goes right, while the Carrie Nation Trail stays straight. (Note: as of September 2011, there were no signs here mentioning the Carrie Nation Trail by name).
Follow the Carrie Nation Trail about 0.3 mile, sometimes walking within the stream itself which may be flowing. The trail angles right out of the drainage, goes left along a ridge and then re-meets the upper stream near some old mining equipment. The mine itself is a few feet farther on. Here, the trail “ends”, according to the map.
Cross the stream and catch the continuation of the trail as it gains up a slope. Just stay on this trail (not shown on the map). It eventually leads up to the ridge south of point 7139, then continues on up to meet the Agua Caliente Trail directly north of Jack Mountain. The trail is easy to follow but pay attention to a few junctions along the way. When in doubt, go up and right.
Now on the Agua Caliente Trail, go right and walk maybe 0.2 mile to an un-named saddle at about 7,300 feet west of Jack Mountain. There is a substantial trail veering off to the ridge, although it is not marked in any manner. This is the unofficial access trail to the observatory road. This trail is pretty good but slightly overgrown. Follow it for about 0.5 mile and 500 vertical feet, aiming for a set of transmission dishes. These sit atop a building off a spur road from the main summit road.
From here, just walk the summit road to the top. This portion covers over a mile and about 700 feet of gain. The highpoint seems to be a natural pile of rocks around the back of the service garage/power plant that is nearby the main observatory building. This pile is about roof high.
The public is welcome to visit the observatory. There is a picnic area with restrooms and even a cola machine slightly lower down near the dormitories.
The total one-way mileage is about 4.5 and about 3,100 vertical feet of gain. Looking at the map, you can plot out a number of alternative approach routes and loop options. Navigation is easy but pay attention to some of the trail junctions as they can be not as obvious as you might expect.
To drive the road, exit I-19 at Arivaca Junction and follow the frontage road south to the town of Amado. The observatory road takes off from here. I did not come this way. It seems to be popular with bicyclists. Beware: the road is narrow and steep in spots.
Usual hiking clothes.
Summer: Can be warm, so get an early start. Beware thunderstorms in late summer.
Fall: Superb conditions usually. Dry, stable weather, cool but not yet snowed in.
Winter: snow may shut access for days or weeks but usually someone has plowed in a route.
Spring: Variable. Can be muddy with late-season snowmelt. Very nice later in spring (April-June)