Run the River: Rio Colorado Ultra Slam™
About the race
The Rio Colorado Ultra Slam is a journey that tracks the spectacular geographical transformation of Texas. Runners trace the lifeblood of the Lone Star State, moving from the rugged granite cliffs of the Hill Country, through the sandy loam of the Lost Pines savannah, and on to an endurance challenge on the edge of the Gulf of Mexico.
From Tow, near the Canyon of the Eagles on Lake Buchanan, to the Colorado River's mouth at Matagorda Bay, the river carves a path of approximately 431 to 432 river miles. The Ultra Slam challenges you to cover this distance on foot, with a challenge distance of 400 miles in one year.
Only 50 athletes will be accepted into the Ultra Slam 200, only 25 into the Ultra Slam 400, and a limited roster into the Ultra Slam 150. Once the roster is set, it is closed.
What you get
- Entry into all your chosen races
- Custom Rio Colorado Ultra Slam finisher buckle
- Series jacket with tier designation
- Ultra Slam bib number carried across all events
- Your name on the permanent Rio Colorado Ultra Slam finisher wall
How it works
- Select your races at checkout (you can adjust up to 60 days before each race).
- Show up. Finish. Repeat.
- Receive your finisher buckle upon completion of your tier.
Your qualifying finishes are tracked automatically, and you will receive a confirmation email after each race showing your progress.
Season dates and roster
2027 season: races run January 1 through December 31, 2027.
Once the roster is set, it is closed.
Fine print
- The 2027 season runs January 1 through December 31, 2027.
- All races must be completed within the 2027 calendar year.
- Backyard ultras must reach the qualifying distance (50 miles for the 200 tier, 100 miles for the 400 tier) to count. Backyard ultras do not count toward the Ultra Slam 150.
- Entrants who do not complete the required races receive credit toward individual race finishes but do not earn the Slam buckle or jacket.
Cancellation policy
Athletes can cancel their registration, but no refund is given.
Entry fees are non-refundable. Injury deferral to the following year's event or another race on the calendar, requested in writing before race day. Race transfers handled at the Race Director's discretion.
The course
The Ultra Slam is a series of qualifying races completed within the 2027 calendar year, chosen by the athlete from a list of races. The 150 tier requires five completed 50K trail races. The 200 and 400 tiers require four completed races of 50 miles or 100 miles each. Backyard ultras count toward the 200 and 400 tiers only.
Three ways to earn it
Note: Backyard ultras count toward the Ultra Slam 200 and 400 tiers only, when you reach the required distance (50+ miles for the 200, 100+ miles for the 400). Backyard ultras do not count toward the Ultra Slam 150, which requires five completed 50K trail races.
Qualifying races
Choose your required number of races from the following, to be completed within the 2027 calendar year.
50K tier (Ultra Slam 150)
- Austin Solstice Circuit
- Labor Day Trail Challenge
- Autumn Harvest
- Colorado River Run
- Star of Texas
- Canyon of the Eagles
- Lost Pines
- Bluebonnet Trail
50+ mile and 100+ mile tiers (Ultra Slam 200 and 400)
- Austin Solstice Circuit (52 Miler or 12-Hour Solo)
- Big Bastrop Backyard Ultra
- Colorado River Run (50 Mile, 100K, 100 Mile or 200K)
- Star of Texas 50 Miler
- Canyon of the Eagles New Year's Trail Challenge
- The Lost Pines Endurance Fest
- Matagorda: The Gulf Coast Backyard Ultra
- Rodeo Trail Run of Austin Backyard Ultra
- Bluebonnet Trail Run 50 Miler
- Austin's Backyard Ultra
Location
City insight: Spicewood
Spicewood is an unincorporated community in Burnet County, Texas, United States, extending into Travis and Blanco counties. Willie Nelson was living on the Luck Ranch in Spicewood in 2020. The climate is humid subtropical, with long, hot summers and mild winters, so spring and autumn are the best seasons to race.
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