Bike the Cuyuna Mountain Bike Trails through the Cuyuna State Recreation Area and the towns of Crosby, Cuyuna, Ironton, and Riverton. Keep track of which trails you've biked on one of the Cuyuna Mountain Bike Trails Maps. The maps are broken down by unit. Get your favorite unit(s), or get them all to create the ultimate Cuyuna Trail map. approximate map sizes: Mahnomen North: 17" x 10" Mahnomen South: 22" x 14" Portsmouth: 31" x 16" Sagamore: 20" x 16" Yawkey: 14" x 13"