Just south of Almo is a great campground called Smokey Mountain Campground, each site has water and electricity, there is a free dump site about 1/2 mile before you enter the park. Closest store is Almo, about 2 miles away. Lots of hiking trails around the park and you can drive up to Emery Pass and watch the rock climbers. Lots of Oregon Trail history in this area so stop the Park Headquarters in Almo to pick up info.
Info found on the internet is confusing. DO NOT turn at the Castle Rock State Park sign. Keep going through Almo. Shortly past the City of Rocks Visitors Center, and just before the pavement ends, take a right to the Smoky Mountain Campground & City of Rocks. Take the first left and follow the road up the hill. The entrance to the CG is to the left. The fee box is just inside the entrance. This is a really nice CG with electric (30 & 50 amp) & water hook ups. Each site is nestled in the Junipers, many have wonderful views of the valley below and surrounding mountains. It is a short drive from Smoky Mountain CG to Castle Rock State Park and City of Rocks National Preserve. Both definitely worth the visit. There is one other very primitive campground a short way down Almo road named Castleview RV Park. This park has no hookups and no trees. The cost is $10 per night. There are also primitive campsites available in City of Rocks. But most are tent only a few can handle small RVs or Vans.