Our first time in the black hills. Can we simply pull into Custer state parks to find first come first service? Like most parks we have found else ware Monday and Tuesdays are better to find open spots? How much are the spots, do they have electric? And experience would be appreciated? 

Looks like THIS will answer some of your questions.

EDIT:

Also found THIS, which says:

  Quote

• Reservations are not required for campsites, but are highly recommended. For summer weekend stays, most campsites and cabins are reserved within a week of reservations opening. Reservations open 90 days before arrival, except at Custer State Park, which accepts reservations one year before arrival. Campsites and camping cabins become available both online and through the call center at 7 a.m. CT / 6 a.m. MT on the first day reservations open. After the reservation window has opened, reservations can be made at any time.

Edited June 18, 2018 by Big5er

I would take their recommendation pretty seriously. The summer we spent at Angostura State Park, near Hot Springs, we spent time with two couples who were hosting the Custer park and they indicated that unused spaces were very rare. On the other hand, Angostura is a park that you can probably get into without a reservation and Shep's Canyon Campground is only about 1/2 hour drive into Custer Park. 

We just drove thru the park 2 wks ago.....noticed one campground had a "reservation phone" at the entrance for same day reservations. All sites in that campground required a reservation but could be made same day.  Many of the campgrounds have electric.  It's a beautiful park, but if you can't get a site in the park there are more nice private RV parks nearby than I've ever seen anywhere!  They really cater to RVers in the Black Hills.  

Whatever you do DO NOT come to Heartland RV Park on Hwy 79 in Hermosa, SD.  THIS PLACE IS A MUDDY MESS! Can't wait to get out of here in 2 days.

  On 6/20/2018 at 9:02 PM, WeBeFulltimers said:

Can't wait to get out of here in 2 days.

Did you review the park in RV Park Reviews and in Campendium ? 

  On 6/21/2018 at 6:30 AM, Kirk Wood said:

Did you review the park in RV Park Reviews and in Campendium ? 

I did in RV Park Reviews but never heard of Compendium.  Will check it out though.