A large township in the extreme eastern portion of Yuba County "amid the beautiful hills of the Sierras". Includes many creeks, the largest of which are Willow, Mill, Clear, Beaver, Oregon, and Mosquito. In some places, snow remains year round, which provided a good supply of water for miners and farmers. There were many rich placer, quartz and gravel mines around Camptonville . The township was named after a large bed of slate in its northern region.
"The Court of Sessions subdivided the county into fifteen townships, August 24, 1850, this section was included in the town of Foster, there being no town of the present name formed. The next division, made August 7, 1851, after the formation of Nevada County, was into eleven townships, the western half of this being in Oak Valley, and the eastern in Goodyear's Bar Township. When Sierra County was taken from Yuba, the court again, Oct 7, 1852, divided the county into ten townships. This time the Slate Range was formed, and included all the present township, except the southwest corner, which was in Foster Bar. It also included all of the present North East Township, lying east of Slate creek."
"The Board of Supervisors again subdivided the county, October 10, 1856, giving to Slate Range all the territory included between the north and middle forks of the Yuba River, and the Sierra county line. August 14, 1858, the line from the mouth of Willow creek to the mouth of Middle Yuba, was changed to a straight line. May 13, 1867, the strip between the Yuba River and the line from Mill creek to a point one thousand feet below the mouth of Oregon creek, was cut off and given to Foster Bar Township."
- Thompson & West, History of Yuba County, 1879
The school in Camptonville was organized in 1855 with 105 pupils. In 1879, the elected trustees of the Slate Range School were J.P. Brown, John R. Meek, and John Ramm
- Thompson & West, History of Yuba County, 1879