It was in Brigham Young's Vanguard Company on 11 May 1847, at a location three-fourths of a mile north of the confluence of the North and South Platte Rivers, that a "roadometer" was attached to a wagon owned by Heber C. Kimball and driven by Philo Johnson. After being attached and used first on the morning of 12 May 1847, it continued to be used during the rest of their journey to the Salt Lake Valley. The 1847 pioneers did not "invent" the roadometer, but the version they created was accurate enough for William Clayton to later use the recorded mileage in his famous Latter-day Saints' Emigrants' Guide.
11 May 1847
"Brother Appleton Harmon is working at the machinery for the wagon to tell the distance we travel and expects to have it in operation tomorrow, which will save me the trouble of counting, as I have done, during the last four days..." Read More
Appleton Milo Harmon
Arose in the morning as usual at the blast of the winding horn. got up our teams & started on our way and crossed the Looking glass crick about one mile from whare we ware camped and travled about 3 miles when we seen a lone indian approaching toward us from [a] narrow skirt of timber . . ." Read More
8 May 1847
All the sights of Buffalo that our eyes beheld [this] was enough to astonish man. . . . The face of the earth was alive & moving like the waves of the sea (Wilford Woodruff's Journals, 1833–1898, typescript, ed. Scott G. Kenney, 9 vols. , 3:171).