Hi Pen, I don't think this family is the one you're looking for since John and Margaret were born in New Brunswick, Canada. Also their Maggie married a John Monroe.Here's the details.
In 1900 John and Margaret and some of their family were living in Union, Humboldt Co., CA. John Smith, b. Canada-English [New Brunswick was stated on the 1880 Census], 67, b.=April 1833, imm 1857, naturalized, marr 32 yrs, farmer. Margaret D., wife, b. Canada-English Dec 1845, had given birth to five children but four alive in 1900, imm 1870. Herbert, son, b. CA Sept. 1871, single, woodsman. John, son, b. CA Sept. 1879, single, farmer. John Monroe, sonlaw, b. IA Oct 1870, marr 5 yrs, farmer. Margaret Monroe, dau, b. CA Oct 1874. Wilber Monroe, grandson, b. CA May 1898. Babe Monroe, grandson, b. CA Nov. 1899.
I also found Herbert and John in 1920 living in American, Sacramento Co., CA.
I didn't find anything for the family members.
You can contact the Redwood Genealogical Society, Inc., cagenweb.com/humboldt/resource.html if you want to pursue information about the Smith family in Humboldt Co. Successful Searching!