His parents later moved their family to Iowa, where Neff completed his education and learned the blacksmith trade.

As an adult, Neff resided primarily in Placer County, where he had large mining interests.

[1] Neff moved to California during the 1849 gold rush, and he worked as a miner until 1863, when he had accumulated enough capital to become involved in other business ventures, including ownership stakes in several mines, construction of a toll road and bridge across the Bear River, and a general store in Dutch Flat Station.

After completing his senate term, he carried out an appointment as a member of the federal commission tasked with inspecting the new Oregon-California Railroad.

Beginning in 1877, he served for 10 years on the board that oversaw California's state prisons.