If you've driven West on AZ-86 out of Tucson you've probably seen Kitt Peak off the side with all the observatories on top. The peak falls on the Tohono O'odham Nation grounds. There is a road you can drive up Kitt, but why drive when you can hike. There an old Jeep road that you can take that will get you to the top as well. It's marked for Emergency use only, so don't plan on driving it or seeing other people along the way.
The road is clear from the parking area and has a nice steady grade on the way up. The average grade is 13% so it's enough to get your heart beating, not to make you want to turn around. There is plenty of cactus and nice views along the way. To the South you have a great view of Baboquvari.
Near the top you will begin seeing the observatory. The observatory is considered to be part of the National Optical Astronomy Observatory (NOAO), although some of the telescopes located here, like those at the MDM Observatory, belong to other groups such as the University of Arizona's Steward Observatory. With 23 telescopes, it is the largest, most diverse gathering of astronomical instruments in the world.
Once near the top you'll hit the main road. Just head a couple hundred yards up and another short scramble and you'll be on top. The hike was shielded nicely from the wind but it wasn't up top. There is a small antenna up and a peak register in a can.
Overall it's a nice little hike that still gets you 3k' feet of gain with relative ease, as you are just walking a dirt road. There is no water anywhere on the hike so bring your own.
To hike Take I-10 South out of Phoenix. Once in Tucson merge onto I-19 South, go 1.5 miles and head West on Ajo Way/AZ-86. Take that 38.7 miles to the turnoff for Kitt Peak AZ 386 turn left (South), head 2 miles and there the main road will curve to the right, head straight here onto a dirt road. Take that another mile or so to a clearing/pit and park there.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.