These are the most popular given names in the United States for all years of the 1940s.
1940
Males James Robert John William Richard Charles David Thomas Donald Ronald Females Mary Barbara Patricia Carol Judith Betty Nancy Maria Margaret Linda
1941
Males Robert John James William Richard Charles David Thomas Ronald Donald Females Mary Barbara Patricia Carol Linda Judith Sandra Maria Betty Nancy
1942
Males James Robert John William Richard Charles David Thomas Ronald Joseph Females Mary Barbara Patricia Carol Linda Nancy Betty Sandra Maria Judith
1943
Males James Robert John William Richard David Charles Thomas Ronald Michael Females Mary Barbara Patricia Linda Carol Sandra Nancy; Sharon (tie) Judith Betty
1944
Males Robert James John William Richard David Charles Thomas Michael Ronald Females Mary Barbara Patricia Linda Carol Nancy Sandra Sharon Judith Maria
1945
Males James Robert John William Richard David Thomas Charles Michael Ronald Females Mary Linda Barbara Patricia Carol Maria Sandra Nancy Sharon Susan
1946
Males James Robert John William Richard David Michael Charles Thomas Ronald Females Mary Linda Patricia Barbara Carol Susan Nancy Sandra Maria Sharon
1947
Males James John Robert William Richard David Michael Thomas Charles Larry Females Linda Mary Patricia Barbara Sandra Susan Maria Carol Nancy Sharon
1948
Males Robert James John William David Richard Michael Thomas Charles Ronald Females Linda Mary Patricia Barbara Susan Maria Carol Nancy; Sandra (tie) Sharon
1949
Males James Robert John David; William (tie) Michael Richard Thomas Charles Larry
Females Linda Mary Patricia Barbara Susan Sandra Maria Nancy Carol Sharon
See also Popularity of birth names for females (United States)
References Most Popular 1000 Names of the 1940s from the Social Security Administration