Daniel P. Barnum was enumerated together with his parents and siblings in the US Censuses of 1860, 1870 and 1880. The 1890 Census was destroyed by fire.
Daniel was married about 1883 to Ann F. Dobbins. He fathered three children with her between 1884 and 1888 and was widowed by the time of the 1900 US Census.
In the US Census of 1900 for District 59, Denver, Arapahoe County, Colorado the family of Daniel P. Barnum was enumerated as follows:
Dwelling #129; Family #137 (700 29th Avenue East)
Barnum, Daniel P.; Head; W; M; b. Feb 1857; 43; Widowed; b. New York; Father b. Connecticut; Mother b. New York; Manager cracker factory; Can read, write and speak English; Rents non-farm home
Barnum, Daniel; Son; W; M; b. Apr 1884; 16; Single; b. Colorado; Father b. New York; Mother b. Illinois; At school for nine months during the census year; Can read, write and speak English
Barnum, Maud; Daughter; W; F; b. Aug 1886; 13; Single; b. Colorado; Father b. New York; Mother b. Illinois; At school for nine months during the census year; Can read, write and speak English
Barnum, Earl; Son; W; M; b. Nov 1888 11; Single; b. Colorado; Father b. New York; Mother b. Illinois; At school for nine months during the census year; Can read, write and speak English
Gifford, Dorothy; Housekeeper; W; F; b. May 1875; 25; Single; b. Michigan; Father b. unknown; Mother b. Michigan; Housekeeper; Can read, write and speak English
In the US Census of 1910 for District 56, Denver Ward 2, Denver County, Colorado Daniel P. Barnum and two sons were enumerated as 3 of the 28 lodgers in the home of Amelia and William A. McWilliams, as follows:
Dwelling #1322
Barnum, Daniel P.; Lodger M; W; 53; Widowed; b. New York; Father b. Connecticut; Mother b. New York; Speaks English; Credit manager; [industry or establishment illegible]; Wage earner; Able to read and write
Barnum, Daniel G.; Lodger M; W; 16; Single; b. Illinois; Father b. New York; Mother b. Illinois; Speaks English; Driver; [industry or establishment illegible]; Wage earner; Able to read and write
Barnum, Earl F.; Lodger M; W; 21; Single; b. Colorado; Father b. New York; Mother b. Illinois; Speaks English; [trade or profession illegible]; [industry or establishment illegible]; Wage earner; Able to read and write
Daniel's son Daniel G. Barnum was enumerated in the 1910 US Census in Shreveport, Louisiana. Neither Daniel P. Barnum, his son Earl T. Barnum, nor his daughter Maude Barnum have been found in any US census subsequent to 1910. Daniel himself is known to have moved to Mexico, where he remarried and lived until his death in 1947.
He moved to Mexico in 1912 as an employee of the Pierce Oil Company, and at the time of his death was employed as a bookkeeper by Petroleos Mexicanos, the Mexican state-owned oil company.
According to the official record of death issued by the Civil Registry Office, Ciudad Madero, Tamaulipas, México, he died of senility at the age of 92 years.
He was buried in the Municipal Cemetery of Ciudad Madereo, 1st Lot (10 Tramo), by special permission of the sanitary authorities.