Awesome granite canyon in the middle of the state!
Fremont is best known as a trad area, but there are a good number of sport routes here as well. All told, the canyon has several hundred routes, sport and trad.
The area is secluded and remote, but is actually fairly easy to get to by Wyoming standards - all paved roads will get you to the place.
The canyon is a deep cleft cut by the North Platte River, and many routes require you to rappel off the rim to get to the base of the climb. The routes often start on a ledge or hanging belay just above the river. There are also a fair number of scrambly hikes into the bottom of the canyon to get to the base.
The canyon proper is typically 200 to 500 feet deep, so there are many multipitch routes.
There are also a pretty fair number of odd side canyons and outcroppings offering shorter routes.
From Casper,take Hwy 220 southwest about 30 miles to the Alcova exit. Exit left (south)and go about 7 miles to a fork in the road. Bear right at the fork. In three more miles you get to the bridge over the canyon and a viewpoint/picnic area.
Casper is the place to stop for decent food, all your gear needs, and beta on Fremont Canyon.
Mountain Sports is the area place to go for gear and beta. Many local climbers work here and are happy to spew info.
5150 climbing gym has indoor climbing as well as gear and beta. Contact the owner for guided climbing throughout Wyoming. The owner will soon publish a new guide book for the area as there are new routes going up in Fremont Canyon.
Slone's in Alcova is the closest place for general needs. They have sack lunches to go.
To expand on the answer given Trask: Steve Petro was only one of the "major players." Arno Ilgner, Kelly Moore, and Pat Parmenter were also heavily involved in developing a high standard in the area. later on, Steve Bechtel played a part.