About this Race Series
Rio Colorado Ultra Slam™
Ultra Slam 400
The 100 Mile Tier. Four races. 400 miles in one year. The pinnacle.
The Ultra Slam 400 is the pinnacle of the Rio Colorado series. Four 100 mile races within a single calendar year. The distance approximates the full 431 to 432 river mile length of the Texas Colorado, from headwaters to Gulf. This is not for the curious. This is for the committed.
How to Earn It: Complete four qualifying races of at least 100 miles each within the 2027 calendar year. Backyard ultras count when you reach 100+ miles (24 yards or more). Limited to 25 athletes.
Qualifying Races
Select any four of the seven races below that offer a 100 mile distance or a backyard format capable of reaching 24+ yards. Click any race name to view course details, elevation, aid stations, and registration for that specific event.
Big Bastrop Backyard Ultra ›
Bastrop. Last Runner and Last Rucker Standing formats. Reach 24+ yards to qualify.
Colorado River Run 100 Mile ›
The namesake race. 100 mile distance along the Colorado River.
The Lost Pines Endurance Fest 100 Miler ›
Bastrop's iconic pine forest. 100 mile distance through sandy loam and singletrack.
Matagorda: The Gulf Coast Backyard Ultra ›
The Gulf Coast finale. Backyard format on Matagorda Bay, the mouth of the Colorado River. Reach 24+ yards to qualify.
Rodeo Trail Run of Austin Backyard Ultra ›
Austin backyard ultra with rodeo flair. Last Cowboy or Cowgirl Standing. Reach 24+ yards to qualify.
Austin's Backyard Ultra ›
The original Austin backyard. Last one standing wins. Reach 24+ yards to qualify.
Backyard scoring: Each yard equals approximately 4.167 miles. You must reach at least 24 yards (approximately 100 miles) at a single backyard event for it to count toward your Ultra Slam 400.
2027 SEASON | Races run January 1 through December 31, 2027
Pricing
| Tier | Early Bird Price | Regular Price |
|---|---|---|
| Ultra Slam 400 | $1,345 | $1,395 |
Your Ultra Slam 400 entry is a single bundled fee that covers all four of your chosen 100 mile races. Payment plans are available at checkout: three monthly installments. Race swaps are permitted up to 60 days before the event date of the race you are dropping, subject to availability.
What You Get
- Entry into all four of your chosen 100 mile races
- Custom Rio Colorado Ultra Slam 400 finisher buckle
- Series jacket with Ultra Slam 400 tier designation
- Ultra Slam bib number carried across all four events
- Your name on the permanent Rio Colorado Ultra Slam finisher wall
FOUNDING ATHLETE PRICING
(Year One Only)
This is the inaugural year of the Rio Colorado Ultra Slam. Founding athletes lock in the lowest price this series will ever offer and get their name on the permanent founders wall at Rio Colorado headquarters.
Only 25 Athletes Will Attempt This.
Fewer Will Finish.
Are you one of them?
Register for Ultra Slam 400
Limited to 25 athletes. Founding pricing available while spots remain.
400 MILES IN ONE YEAR.
Contact Information
If you have any questions about this race series or its scoring, please use the following email address:
Included Events
The Lost Pines Endurance Fest
Lost Pines 100 Miler
Saturday January 16, 2027
Bastrop, TX US
Matagorda: The Gulf Coast Trail Running Festival
Gulf Coast Backyard Ultra
Saturday February 13, 2027
Matagorda, TX US
Rodeo Trail Run of Austin • Backyard Ultra (Last Cowboy/Cowgirl Standing) • 8 Hour • Marathon • Half Marathon • Backyard Ultra Relay Duos (2-Person Team)
Rodeo Backyard Ultra
Saturday March 13, 2027
Spicewood, TX US
Austin's Backyard Ultra • Marathon • Full • Half & Memorial Day Remembrance Run 4 Miler • 8 Miler
Austin's Backyard Ultra
Saturday May 29, 2027
Marble Falls, TX US
