James Calvin Sly Sr.

from D.U.P. #547:
While traveling further east, several of the men found a pleasant mountain meadow with a stream near Pollack Pines that was ideal for grazing cattle. One of the men, James Calvin Sly, carved his name on a tree trunk, which became a landmark and gave the area its name, Sly Park. Sly Park became the final rendezvous point for the group. The party included 43 men, 1 woman, 1 small cannon, 17 wagons, 150 horses, and 150 head of cattle.

from findagrave:
James Calvin Sly was born in Ontario County, New York – which is now known as Wayne County.
He was buried in the cemetery of Chicken Creek, UT but the grave was washed away in a flood.
He was in Mormon Battalion Company B.
Sly Park Valley, Sly Park, Sly Dam in Placerville, El Dorado County, CA are named for him.*
He was a miller at Sutter’s Fort where the gold was discovered that started the California gold rush.
He was an explorer, scout and much, much more.

from the plaque in Bountiful City Park:
During the summers of 1849 and 1850, more than 25,000 emigrants passed this way en route to the California gold fields.  The vanguard of the 1849 emigration reached Great Salt Lake City about June 16th.  They lingered in the city to rest their animals and buy supplies.  The first forty-niner wagons to pass here on the way to City of Rocks were led by James C. Sly, a Mormon Battalion veteran.