1878 April 18, 4th Class Lake Mountain, Trinity, California Post Office established located 14 miles south of Hoaglin and 25 miles north of Covelo. The nme was derived from the Lake mountain Ranch.
W.S. ? Ferguson, First Postmaster.
1878 April 22, San Francisco Bulletin, Pacific Coast Postal Changes - Postoffices Established - Lake Mountain, Trinity county, N.J. Ferguson, Postmaster.
1878 May 24, P O discontinued.
1909 August 3, Post Office re-established.
1917 August 31, P O discontinued.
1920 April 28, P O re-established.
1923 February 15, P O discontinued.
1936 September 1, Post Office -re-established as P O moved from Hoaglin.
1953 July 31, P O discontinued and the service moved to Covelo in Mendocino County.