Dewitt was of “Yankee” stock, the Colman family having been in Massachusetts since at least the early 1700s and the Main family in Stonington CT before 1670. Dewitt’s great-grandfathers, Job Colman and Peter Main, both fought in the Revolutionary War. His grandfather Samuel Colman had settled in the Springfield "wilderness" about 1794.
Dewitt’s only known sibling, a sister Cynthia M. was born in 1828. The 1840 census indicates another girl under 5 in the household, but no information has been found on this child.
The 1830 census paints a picture of the geographic relationship of the extended Colman family in Springfield. Dewitt's uncles Hamilton and Nelson were listed adjacent to his grandparents Samuel and Abby. Horace and his brother, Franklin, are listed in the "neighborhood" only two households away. His uncle Nelson Colman and his other grandfather, Joseph Main, appears on the same census page as well.
Dewitt’s mother, Polly, died on 23 January 1844, when she was 44 years old. She was buried in the Drake family cemetery on Thurston Hill, overlooking Otsego Lake. Before the year was out, 22 year-old Dewitt married in November 19 year-old Mary Haith or Heath, a Springfield resident, born in Lincolnshire, England. They began their family in Springfield. Children included:
- Mary b. 1845
- Joseph b. 23 April 1847
- John Herbert b. 5 October 1851
- Lucien & Lucius b. 31 March 1854
About 1854 Dewitt's growing family moved to Cooperstown, in the town of Otsego. The 1855 NYS census lists their five children, and Ann Heath, dressmaker, Mary’s 17 year old sister. Their home is shown in the upper left of the Beers Map.
More children were born in subsequent years:
- Horace b. 4 April 1856
- Fenimore b. 2 May 1858
- Alice Worthington b. 6 August 1860
- Ellen b. 22 November 1861
- Edith b. 22 November 1862
- Charles Gregory b. 15 May 1864
The children are listed in the records of Cooperstown’s Christ Church (Episcopal). Edith died as an infant on 14 June 1863 of scarlet fever.
The family operated a saw mill on the Susquehanna River at Mill Street. Dewitt’s occupation is listed on the 1860 census and following years as “sawyer.” The 1868 Beers Atlas shows the family home on First Street, now River Street, near the Otsego town line, which had been bought from William Schmidt late in 1867 for $1,000.
In 1870 Dewitt bought land from Dorr Russell in Middlefield, just across the river from the village of Cooperstown. His holdings included a 4.5 acre parcel on the east side of Brooklyn Avenue and 18 acres on the west side, abutting the Susquehanah River.
Dewitt’s oldest son Joseph died 17 June 1869 of inflammatory rheumatism. At 22 years old, he was also working at the mill.
In the 1870 census, mother-in-law Sarah Heath was living with Dewitt and Mary, upon the death of her husband George. Daughter Mary had married George Becker in 1865 and was listed next on the census form with children Carrie b. 1868 and later Lucy b. 1873. Sarah Heath/Haith died in 1874 and was buried in Springfield Center.
Dewitt is listed in the 1872-3 County Directory as head sawyer with Johnson Brothers. When the property was sold by Francis Johnson to the Cooperstown Aqueduct Association (water department) in 1879, the sale was subject to the lease to D. C. Colman.
In 1880 Lucian and John were married and lived nearby, Alice, at 20, may have married and moved out, and the remaining four children still lived at home. The 1880 census includes neighbors Dorr Russel and Dennis Heath as well as son John Coleman and his family, which included Dewitt's father, Horace. Dewitt and his sons John, Horace and Fenimore all listed their occupations as “sawyer.” The 1880 and 1892 census list the Colmans as Middlefield residents. Dewitt’s father, Horace, died in 1884 and was buried in Lakewood cemetery.
Baseball must have played an important part in their recreational life. Son John was said to be the only pitcher in the county to throw a curve ball, and he and his catcher Horace were asked to try out for the Philadelphia Athletics in the 1880’s. Fenimore was also on their town team, which played games on the field adjacent to their homes.
In 1895 Dewitt and Mary lived with son Charles, his young wife and son Albert. At that time sons John, Horace, and Lucius were all neighbors.
Dewitt and Mary celebrated their 50th wedding anniversary at a party in 1894.
Dewitt died on 13 July 1896 in Cooperstown at the age of 74. The cause of death was carcinoma of the face. His occupation is listed as “farmer” on his death certificate. His land was transferred to his son Fenimore. He was buried in Lakewood cemetery. Mary died four years later. The family marker includes Dewitt, Mary, and their children Edith and Joseph. His father, Horace is buried in the same plot.