Spring Mountains National Recreation Area lies to the west and north of Las Vegas. They're adjacent to Red Rock Canyon National Conservation Area, but are in the Humboldt-Toiyabe National Forest. Of course, the Humboldt-Toiyabe consists of a series of discontinuous tree-covered ranges that divide the various basin regions of Nevada. The national forest has patches scattered over virtually every end of the state.
I got there around 8am. At that time, there was plenty of parking. And I only passed maybe a dozen people coming in. There were a lot more on the way out, but it was still not hard to get away from it all.
About four miles for the day. It's about 20 degrees cooler up here than in Las Vegas, by the way. It's a nice place to get away from the Strip, if you're looking for cooler outdoor recreation in the summer in Las Vegas.