Registration for the Mines of Spain 100 trail races is hosted on and opens each year on January 1st at midnight CST.

EARLY – 1/1 through 1/31 – $200 (100mi) – $125 (100k)
REGULAR – 2/1 through 6/30 – $225 (100mi) – $150 (100k)
LATE – 7/1 through 10/1 – $250(100mi) – $175 (100k)

All registrations include a guaranteed donation to the Friends of the Mines of Spain as a way to help support nature & conservation education, volunteer programs and park projects at the Mines of Spain.  Please consider becoming a Friend of the Mines of Spain by following this link.

The deadline for guaranteed swag size is a month out from race day.

If the MoS100 will be your first 100 mile finish, use discount code ‘virgin’ to take $20 off your registration. It doesn’t matter whether you’ve DNF’d or DNS’d in the past, the discount applies as long as you’ve never finished 100 miles or more in an official endurance running event (distance, timed or otherwise). We hope that you’ll share the magic, excitement and life long memories of an accomplishment like running 100 miles with us at the Mines!

If you are a military veteran and have served or are serving in the United States Armed Forces, use discount code ‘veteran20’ to take $20 off your 100 mile registration or ‘veteran10’ for $10 off your 100k registration. This is just one small way that our race can thank you for your service to this country. If you are both a veteran AND a 100mi virgin, use ‘virginveteran’ for a combined $40 discount!

Please note for both virgin and veteran discounts, codes are valid as long as online registration is open/available and MUST be used at time of registration. Discounts are not available retroactively if a runner forgets to use when registering.

No proof of either Virgin or Veteran status will be required. But rest assured, due diligence on the part of the race will be exercised in determining the validity of either claim and anyone found to be falsely identifying as a 1st time 100 mile finisher or especially as a US military veteran will be immediately disqualified on race weekend, given NO refund of any sort and banned from all future events. In addition to this, your name will be provided to the internet with a description of your attempted fraud.

Partial refunds and deferrals are available if the race is notified in writing ( and the runner receives a reply confirming the request.

The deadline (end of day) to request a refund/deferral is:
100% deferral or 50% refund – June 30th
75% deferral – August 31st

If a runner becomes pregnant or gives birth after registering for the event, that runner is eligible for a 100% deferral up through the final August 31st deadline listed above. The runner must notify the race in writing ( and receive a reply approving the request. While not required, the race reserves the right to request additional documentation from a physician, registered midwife or other medical professional.

All deferral credits are good for TWO years (2024 or 2025) and are not transferrable to another runner. Please note, any deferred registrant MUST still complete the registration process and a deferral credit can only be used ONCE. If used in the first year available, it can NOT be used a second time. The deferral credit is a rollover discount of whatever you paid in the year you deferred. The window to register using your rollover credit for 2024 will close January 31st. If you do decide to wait and use it for 2025, the same process will be repeated in January of 2025 at which point you’ll have that month to take advantage of the credit before it expires.

NO refunds after June and NO deferrals after August.
NO bib transfers.
Any runners who withdraw after August may still pick up their packet Thursday evening at the latest. No packets will be mailed.

The race reserves the right to modify the course for matters related to runner safety or trail condition concerns or to cancel the race in the case of natural disaster, global pandemic, etc. In situations like these, we will do our absolute best to take care of our runners as we always have in the past but there will be no guarantee of refund of registration fees.

Please DO NOT register if any of this is unacceptable to you. Severe Weather Policy

Runners are allowed to switch distance after registration by contacting the race directly. If switching from the 100k to 100mi, you will be required to pay the difference in registration cost. Switching down does not cost anything additional but does not issue any refund. The deadline to switch up to the 100mi is September 15th. You are allowed to switch down to the 100k through Thursday night pre-race packet pickup.

When the race reaches capacity, a waitlist will be maintained publicly on ultrasignup and participants on the waitlist will be invited via email as spots open in the order they signed up. Invited runners will be given 5 days to either accept or decline before their spot is passed on to the next runner.  Four weeks out from the event, that 5 day window will shorten to 48 hours. This is to be fair to other runners still on the waitlist.

There is no qualifying requirement to register but we strongly recommend any 100mi runner complete a minimum of a 50 mile trail race and any 100k runner complete a minimum of a 50k trail race in the preceding 12 months leading up to the race. Similarly, there is no service requirement but we encourage all runners to give some of their time and energy by volunteering at local races, participating in trail work opportunities or just giving back to the trail community in whatever manner they’re able to. Don’t have the time or opportunity? Make a monetary donation to your area trail conservation organization. Good trail karma always comes in handy!

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