These are the most popular given names in the United States for all years of the 1900s (decade).
1900
Males John William James George Charles Joseph Frank Henry Robert Harry Females Mary Helen Anna Margaret Ruth Elizabeth Marie Rose Florence Bertha
1901
Males John William James Joseph George Charles Frank Henry Robert Edward Females Mary Helen Anna Margaret Elizabeth Ruth Marie Gladys Florence Rose
1902
Males John William James George Joseph Charles Robert Frank Edward Walter Females Mary Helen Anna Margaret Ruth Elizabeth Marie Lillian Florence Alice; Rose (tie)
1903
Males John William James George Joseph Charles Robert Frank Walter Henry Females Mary Margaret Helen Anna Ruth Marie Elizabeth Florence Dorothy Lillian
1904
Males John William George; James (tie) Joseph Charles Robert Frank Edward Walter Charlie Females Mary Helen Margaret Ruth Anna Dorothy; Elizabeth (tie) Marie Alice; Florence (tie)
1905
Males John William James George Charles Joseph Frank; Robert (tie) Edward Thomas
Females Mary Helen Margaret Anna Ruth Dorothy Elizabeth Mildred Lillian Marie
1906
Males John William James Joseph George Charles Robert Frank Henry Edward Females Mary Helen Margaret Ruth Anna Elizabeth Dorothy Marie Alice Florence
1907
Males John William James George Charles Joseph Robert Frank Thomas; Walter (tie)
Females Mary Helen Margaret Anna Ruth Dorothy Elizabeth Mildred Alice Ethel
1908
Males John William James George Joseph Charles Robert Frank Edward Henry Females Mary Helen Margaret Anna Ruth Dorothy Elizabeth Mildred Frances Florence
1909
Males John William James George Joseph Robert Charles Frank Edward Henry; Walter (tie) Females Mary Helen Margaret Ruth; Dorothy (tie) Anna Elizabeth Mildred Marie Alice
See also Popularity of birth names for females (United States)
References http://www.ssa.gov/OACT/babynames/index.html http://www.ssa.gov/OACT/babynames/decades/names1900s.html