Hi, I found Robert L Cooper in the 1930 Census in Pinedale, Sublette,Wyoming.
Born About 1918 In Colorado.

Owned a Residence on Lake St.
Parents are:
Lee E. Cooper - Born 1883 in California
Occupation is Manager at lumber mill

Pearl Cooper - Born 1887 in Ohio.
Occupation Stenographer in lawyer's office.


In 1920 Census:
Wyoming > Fremont > Election District 6
Listed is:
Lee E. Cooper
Pearl M. Cooper
Robert Lee Cooper - 1 yr 9 M.

Lee Cooper is listed as supervisor of Forest Service.

Anything else Please contact me.

Age when married:
Lee E. Cooper 30 yrs old
Pearl Cooper 26 yrs old

1930 Census says that Lee's father was born in Michigan and his mother was born in Illinois.
Pearl's Father was born in Ohio and Mother Ohio.

 

Source: 

  1. Ancestry.com message board

  2. Ancestry.com message board