I grew up in nearby Kearny, so Steamboat Mountain always fascinated me. It is made of limestone - built layer upon layer by an ancient sea. Fossils from various sea creatures can be found in the boulders that have fallen from its cliffs. The mountain is slowly coming apart, as evidenced by some large cracks found on the summit.
Steamboat Mountain is part of the Dripping Springs Mountain chain, which is situated on Pinal/Gila county line. It is in the eastern portion of the Sonoran Desert, and I have seen javelinas, rattlesnakes, a desert tortoise and even a gila monster on its slopes. The area is also home to mountain lions, although I've not personally seen one. The area has been thoroughly worked by prospectors, and there are at least two long abandoned mine shafts near the mountain.
There is no trail, just eyeball the route up to the top the best you can. I'm not a cliff climber, so I worked my way up the eastern side of the mountain where access to the summit is easier. There is a large, treacherous rock slide on that side, so make sure you're high enough on the mountain base to avoid it.
From the top, you get a great view of the Gila River Valley to the south, the Dripping Springs mountain range to the east and west, and the Pinal Mountains to the North. The town of Kearny is visible in the distance, and the smoke stack from ASARCO's Hayden smelter can be seen to the east. The wash on the western side of the mountain has a seasonal waterfall, and there are a couple of canyons with springs to the north. These canyons have tall cottonwood trees and very lush vegetation.
To hike Take US 60 east from Phoenix all the way to Superior. Turn right on state route 177 to Kearny. Turn left on dirt road that leads to the two water tanks just past the turn off to Kearny's business district. The dirt road is about 8 miles long and will take you all the way to the base of Steamboat Mountain.
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.