The Orange Curtain 100 km race is a 10 kilometer out and back (repeated 10 times) along a 5 kilometer segment of the asphalt and dirt bike path on the east side of the San Gabriel River in Cerritos, Lakewood, and Long Beach, California. The race course starts just south of South Street in Cerritos and travels south 5 km to a point midway between Wardlow and Spring streets.

Most (90%) of the bike path has a dirt path alongside. The 10% lacking the dirt path is mainly the 3 underpasses at Del Amo, Carson, and Wardlow. So for most of the course, you have a choice of running on pavement (predominately asphalt) or dirt. The aid station is located right after the Wardlow underpass.

The adjoining San Gabriel River channel is artificially channelled. You may run into a cloud of gnats here and there. Sunglasses will help keep these out of your eyes. There are some stables just south of the aid station so you will see some horses. I have seen a horse on the course but that is rare. It is more common to see ducks and egrets along the course.

Much of the race course is bordered on the east side by Liberty Park (in Cerritos), Rynerson Park (in Lakewood), or El Dorado Park (in Long Beach). One section of the course is bordered by the parking lot at the Long Beach Towne Center shopping mall.