1930 census San Diego Co., California - Chula Vista, Flower Street:
Walter P. Calvin - age 43, age 42 at first marriage - born Illinois, parents born Illinois - owns home - laborer, ice company Agnes - wife - age 28, age 18 at first marrriage - born New Mexico, parents born Germany Glenn C. - son - 9 - born Calif. - father born Illinois, mother born New Mexico Eugene E. - son - 4 - born Calif. - father born Illinois, mother born New Mexico
Next h/h to William Scheibert, 63, born Germany, with wife Katherine, 57, born Germany (maybe Agnes Calvin's parents?)
This Walter Calvin may be the man of that name in 1920 Kansas City, Missouri census, aged 32, born Illinois, divorced, living in a boarding house.
Also, in 1900 census there's a Walter P. Calvin, born Mch 1887 in Illinois, in Missouri household of Lewis and Lucinda/Lucreda Calvin. These are just threads but you could follow up further in a search for "Walter" and his initials and other children's names.
This isn't my family, but I'm researching ARCHIBALD "Archie" CALVIN who emigrated to California from Co. Monaghan, Ireland.