USBR 15 is being designated in segments and will connect the Florida to North Carolina when it is complete. The landscape is rural and mostly flat, with lots of dense greenery and the occasional large open field.
USBR 21 connects Atlanta to the Tennessee border near Chattanooga. It begins in downtown Atlanta at the Five Points MARTA Train Station, connects to the Silver Comet Trail, and follows two-lane country roads through northwest Georgia.
More information from Georgia DOT
USBR 221 is an alternate loop off of USBR 21 that takes cyclists through the Chickamauga and Chattanooga National Military Park.
USBR 421 is an alternate loop off of USBR 21. It connects to Mountain Coves Farm, which provides scenic views of nearby Lookout and Pigeon Mountains and the rolling green hills of the valley.
USBR 621 is an alternate loop off of USBR 21 that connects through the community of Rome.