In the 1880 US Census for District 246, San Jose, Santa Clara County, California the family of Seth L. Barnum was enumerated as follows:
Dwelling #378; Family #386
Barnum, Seth L.; W; M; 46; Married; Retired Grocer; b. New York; Father b. Connecticut; Mother b. Massachusetts
Barnum, Nellie M.; W; F; 39; Wife; Married; Keeping House; b. New York; Both parents b. New York
Barnum, Lizzie M.; W; F; 12; Daughter; Single; Attending school; Attended school within the census year; b. Illinois; Both parents b. new York
Barnum, Olive R.; W; F; 10; Daughter; Single; Attending school; Attended school within the census year; b. Illinois; Both parents b. new York
Barnum, Paul; W; M; 3; Son; Single; b. California; Both parents b. New York
Sosee, Ernest M.; W; M; 22; Stepson; Single; Peddles water filters; b. Wisconsin; Both parents b. New York
In the 1900 US Census for District 141, Green Valley, Solano County, California Seth Barnum was enumerated as follows:
Dwelling #115; Family #116
Lang, Herman; Head; W; M; b. Mar 1854; 46; Single; b. Kentucky; Both parents b. Germany; Can read, write and speak English
Barnum, Seth L.; Cook; W; W; b. Apr 1834; 66; Widowed; b. New York; Father b. Connecticut; Mother b. Massachusetts; Can read, write and speak English
In the 1910 US Census for District 131, San Joaquin, Sacramento County, California Seth was enumerated with the family of his brother-in-law Michael A. Fry and sister Harriet.