The following data is extracted from Days of Yore: Early History of Brown County, Nebraska.
The "Calamus Trail" entered Brown County near the southeast corner. Its eastern terminus was Fort Hartsuff (near Ord). It followed up the North Loup River, then the Calamus River to its source in Moon Lake, then on west through the sand hills to the forts in the western part of the state. It was used chiefly as a military route for United States troops passing from one post to another. In later years a government post was maintained on the north shore of Moon Lake, affording a stopping place for travelers and also a place for securing supplies. (Moon Lake was at first named Post Lake from the fact that this government post was located on its shores. Branches from Calamus Trail led to other places, and these trails and the last traces of the supply post may still be found by diligent search.)
The "Gordon Trail" was made in the spring of 1875 by a large company of gold hunters from Sioux City, Iowa, who were trying to enter the Black Hills against the orders of the government. The expedition kept to the south side of the Niobrara River in order to evade United States troops from Fort Randall (South Dakota), who had been ordered to prevent them from entering the Black Hills. The troops overtook the Gordon party near the present site of Gordon, Nebraska, and destroyed the wagons and other property of the miners who were all placed under arrest and taken to Fort Randall. (There were twenty-nine wagons with four-horse teams, so their trail was well marked. It passed north of Long Pine, then followed quite closely the present route of U. S. Highway No. 20 across the county, passing just north of the courthouse and crossing Bone creek northwest of Ainsworth. This trail and other routes followed by early freight wagons are sometimes called "Black Hills Trails.") All of these dim reminders of by-gone days tell us a story of brave men who ventured into a wilderness, the leaders of a migration that later came in a never ending procession.
In 1857 Lieutenant G. K. Warren of the U. S. Army was sent to explore the Niobrara River. He was equipped with a .few wagons drawn by eight-mule teams and a small force of men. The object of the expedition was to find a practical route for freighting army supplies from Fort Randall to Fort Laramie. That he did not find such a route is a matter of history, though his reports show that he made a thorough exploration of the country adjoining the Niobrara and Keya Paha rivers. (If this expedition left a "trail," I have yet to hear of it.)
Source: Days of Yore: Early History of Brown County, Nebraska