Bear Creek Lake Park · Colorado

One loop.
Every hour.
Until one remains.

Bear Creek Lake Park

The 11th Hour Backyard Ultra is a last-runner-standing race: a 4.16-mile loop, on the hour, for as long as anyone can keep starting the next one. It begins at dusk on Halloween.

Oct 31
Race day
4.16 mi
Per loop
60 min
Per lap, no more, no less
50 spots
$65 entry
Register — $65 See the format

50 spots. Also listed on RunSignUp and UltraSignUp — registration happens here.

The Format

Simple rules. Unforgiving math.

Backyard ultra rules, run at Bear Creek Lake Park. No course record, no age-group awards — just the clock and who's still on the start line.

One wrinkle: the park closes in the evening, so this edition is capped at 11 laps — the final lap starts at 6:00 PM. If the field is still standing at that point, the race ends there rather than running the true last-one-standing format to its natural conclusion.

Each hour

A new loop starts

Everyone still in the race lines up and runs the same 4.16-mile loop. Finish early, and the rest of the hour is yours to eat, sit, or dread the next one.

Miss the gun

You're done

Fail to start the next loop on time, and your race is over. There's no partial credit — only a finish time recorded as your last completed loop.

Last one standing

Wins outright

The race only has an official finisher when exactly one runner completes a loop that no one else does. Everyone else is ranked by loops completed.

Same loop. Same hour. Again.

The Course

Bear Creek Lake Park

A reservoir-side park in Lakewood, Colorado, with the trail network and access needed to run a repeating loop safely through the night — lake views for the daylight laps, headlamps for the rest.

DateSaturday, October 31
LocationBear Creek Lake Park, Lakewood, CO
Start time8:00 AM
Field cap50 runners
Entry fee$65
AidOne station, at start/finish
Lap cutoff11 laps max — final lap starts 6:00 PM