In 1880 Dewitt and Mary had no children. William McCoy, age 13, born in Texas, was living with them - this was apparently the three-year-old that lived with Peter B. in 1870.
Apparently Mary died or they divorced because he married Lou ??? about 1890 according to the 1900 and 1910 Censuses.
Lived in Arkansas City, Kansas, in 1901, according to father's obituary.
1900 Census, Kansas, Cowley Co. Arkansas City, Ward 1
1910 Census. Kansas, Cowley Co, Arkansas City, Ward 1
Not found after 1910.
USGenWeb, Cowley Co, Kansas website shows Dewitt C. Allen, birth date, 20 Jul 1854, buried in the old section of Riverview Cemetery. No death date given. There were five Mary Allens buried there, including one Mary J. Allen. The location of the graves are given and none of the Marys are buried next to DeWitt.
The Civil War pension file of his brother Augustus, includes an application of the widow for reinstatment of her pension and Dewitt Allen, who had testified earlier, in the 1880's, was deceased before 1921 when a special examination of the application was conducted.