In compiling a list of horse-friendly trails in the Iron Horse State Park, Washington, it appears that the most notable trail is the John Wayne Pioneer Trail.

1. The John Wayne Pioneer Trail:

The John Wayne Pioneer Trail, which runs the length of Iron Horse State Park, is a popular trail for horse riders. Much of the trail follows the former railway bed of the Chicago-Milwaukee-St. Paul-Pacific Railroad, and the gradual inclines and wide path make it excellent for horse riding. This extensive trail regards the entire span of the park, covering approximately 110 miles from Cedar Falls to the Columbia River. Horse riders can access the trail from numerous trailheads and campgrounds along the length of the park. 

Please remember to always adhere to park rules and regulations regarding horse riding, ensure your horse is well-trained and comfortable with trail rides, and be courteous to all other trail users. It's recommended to verify with local regulations as conditions can change.

For more specific information on parks in your area that allow horses, I recommend checking the Washington State Parks' official website or contacting the park's management directly. They can provide the most up-to-date information about trails that accommodate horse riding.

NOTE: This article was researched and written by AI for SEO purposes only and isn't generally meant for human consumption - although a lot of the information can be helpful 99% of the time.  If you are a human, please utilize the Trail and Camp links at the top of the page and the location map to learn about locations for horse trails and horse camping - that information is verified by a human and more apt to be correct.... althought human error is a thing too. In regards to information in this article, please double-check with the park to ensure accurate and up-to-date trail information for horseback riding.