Check out http://www.familysearch.orghttp://www.familysearch.org.It has many free databases available for searching.It is run by the LDS (mormon) church and they make their data freely available to everyone for family history research.
A quick search turned up several records:
March 12, 1908 Harry Blackmore, son of Thomas Blackmore and Alice Dickerson married Georgia Donaldson, daughter of William Donaldson and Martha Stewart in Blissfield, Lenawee, Michigan.Harry was 32 and Georgia was 24 and both were born in Michigan.
1910 Census Harry Blackmore b. 1876, Michigan, res. Blissfield, Lenawee, Michigan Spouse: Georgia Blackmore Child: Autumn Blackmore
1920 Census Harry Blackmore b. 1877, Michigan, res. Lenawee, Michigan Spouse: Georgia Blackmore Child: Autumn M. Blackmore Child: Donald R. Blackmore
1930 Census Harry Blackmore b. 1876, Michigan, res. Lenawee, Michigan (Father born England, Mother born New York) Spouse: Georgia Blackmore Child: Autumn Blackmore Child: Donald Blackmore
For the census items I just looked at the head of household so take a look at each person from the census, and the original census forms to make sure there were no transcription errors.
Also, take a look on Ancestry.com.I don't have it at home, it is free at our library -- check it out at your local library.
I found a marriage record for a Thomas Blackmore who married an Ellis Dickerson in Ohio in 1864. On the 1880 census this family is living in Arcadia, Lapeer, Michigan:Thomas Blackmore, born in England married to Ellis who was born in New York, with children: Lily age 12, Rosa age 7, and Thomas H. age 4.I could not find a birth of Harry that tied but I found a Thomas H.F. Blackmore born February 10, 1876 to Thomas and Eliza in Arcadia, Lapeer, Michigan.You'd need to do a little more research to tie all this together.