This method is clumsy but it's one way to find those allusive national forest (NF) campgrounds that accept horses. To the left of this bulletin board/forum are a bunch of tabs. And, just below them, is an icon or item called "Google Search." It is there that I'll show you how to search forestcamping.com for equestrian campgrounds.
Step 1 - In the blank space, type "equestrian" and the name of the state where you want to camp. For demonstration purposes, I'll use Oregon. So, for demo purposes, you have now typed the keywords "equestrian oregon" (w/o the quotes and period). Leave "This Website" enabled.
Step 2 - Click on "Search." Google will search throughout forestcamping.com for the above keyword combination. A Google screen is displayed with the results of your search.
Step 3 - Look for HTM file names with "cmp" in them, e.g., . . . forestcamping.com/dow/pacficnw/umacmp.htm. The cmp denotes the campground description page for, in this demo, the Umatilla National Forest. Click on the title of the paragraph, which in this case, is Umatilla National Forest Campgrounds.
The campground description page on forestcamping.com is displayed listing and describing all the campgrounds surveyed on the Umatilla. You can use your browser search function to search for "equestrian" on the page or simply scroll down looking for "equestrian." Primitive, yep, but it's a source.
An example of one of the campgrounds you'll find is North Fork John Day campground. It briefly describes that there is a loop for equestrian campers along with some communal facilities for horses. If you need more info., call the listed ranger district office or go to the Forest's website (Helpful Links) at top of the page.
I also recommend that you do a second search in Step 1 by typing "horses oregon." Most of the time our research uses equestrian but we did use horse or horses on occasion. Sorry about that. Finally, you could also enable "Web" in the Google search. There might be, among other things, local or state websites that could be useful.
Co-author of the U.S. National Forest Campground Guides