I didn't find a marriage record but this might help.
1900 census: Hamilton William, head, Sept 1870, 29, m 7 yrs, Massachusetts 3x, stenographer - Mary, wife, Mar 1872, 28, m 7 yrs, 1 child born and living, Massachusetts, Ireland 2x, decorater
1910 United States Federal Census about Mary Hamilton Name: Mary Hamilton Age in 1910: 37 Birth Year: abt 1873  Birthplace: Massachusetts Home in 1910: Manhattan Ward 16, New York, New York Race: White Gender: Female Relation to Head of House: Self (Head) [Head] Marital Status: Widowed Father's Birthplace: Ireland Mother's Birthplace: Scotland Neighbors: View others on page Household Members: Name Age Mary Hamilton 37 (She was a lamp shade designer in this census.)
from italiangen death records search: Hamilton William A 34 y Mar 5 1904 8601 Manhattan H543
possibility: Name: William W Hamilton Birth Date: 25 Sep 1870 Event Type: Birth Event City: Yarmouth Father Name: Henry Mother Name: Minerva White