The Oregon Trail, the California Trail and the Mormon Trail all passed by (through) Ft. Laramie.
The Fort Laramie National Historical Site is open throughout the year, usually from dawn to dusk. There has been no entrance fee since 2015. While the final stage of this cache is offsite, you need to be there at times when they are open to be able to determine the final location.
My wife and I started volunteering here last year. During the spring, summer and fall, one day a week, we were in 1880's costume, explaining various facts about the buildings at which we were stationed.
I was at the Post Trader’s Store.
This was a private business at the fort, licensed to sell to the soldiers, settlers passing through and to trade with the local Indian tribes. This building is one of the two oldest, standing buildings in Wyoming. The other is “Old Bedlam”, another building at Fort Laramie. They were both built the same year, so we fight over which is older.
I learned lots of interesting stuff volunteering here. For example, during the peak year of the westward migration of settlers, nearly 60,000 settlers passed by Fort Laramie. That’s just shy of the population of Cheyenne today. And most of them travelled past between beginning of May and the 4th of July. If you arrived earlier than May, the grasses hadn’t grown along the trail to feed the livestock. If you came later than the 4th of July, the grass would have all been eaten by the previous wagon trains' animals AND you might not make it over the mountains before winter set in.
There are interesting bits of information at all the buildings. During a good part of the year many of the rangers give short talks and demonstrations on a variety of subjects relating to the time period that the fort was a military installation. And in the visitor's center you can find a link to download a self-guided walking tour onto your phone. Spend an hour or spend the day.
Now onto the cache. The posted coordinates take you to a monument with a lot of commemorative plaques on it. You will need information on these plaques to find the final coordinates.
The degrees and the first two digits of the final N coordinates are the same as the posted location. (N 42° 12.mmm')
To find the last three digits, find the following information:
A = The number of miles rode by the 120 celebrated riders.
B = The Wyoming Place Number for Fort Laramie on The National Register of Historic Places.
The last 3 digits of the final N coordinates is the number ...
(A÷B)/100 + (A÷B)/1,000 + (A÷B)/10,000
The degrees and the first two digits of the final W coordinates are the same as the posted location. (W 104° 33.mmm')
To find the last three digits, find the following information:
X = The year the Transcontinental Telegraph reached Fort Laramie.
Y = The last year that Fort Laramie was a major station on the telegraph line.
Z = The number of days in February in the year that the Pony Express ended service.
The last 3 digits of the final W coordinates is the number .....
(X+Y)/5 - Z
There is room in the cache for small swag, but bring a pen to sign the log.
There is a small FTF trackable for the First To Find, to keep or send out.
You can validate your puzzle solution with certitude.