Albert Preston Barnum was born in Ohio in 1843 and lived in that state until at least 1861, when he enlisted in the 3rd Regiment, Ohio Volunteer Infantry at the start of the Civil War. At the end of the war he moved west. He was apparently in Missouri by 1869 or earlier and by 1870 he was settled in the New Mexico Territory, where he lived until his death in 1905.

Family tradition suggests that Albert fought in the Civil War on the Confederate side, was captured by the Yankees and was somehow later released. Although the available records do not support that version, there is a grain of truth in the oral tradition. Albert did become a paroled prisoner of war. However, he was fighting on the Union side and was captured and paroled by the Confederates.

On 25 Apr 1861, at the age of 18, Albert P. Barnum enlisted as a Private in Company I, 3rd Regiment Ohio Infantry (3 months' service). He mustered in on 30 Apr 1861 and mustered out of that unit on 22 Aug 1861. He immediately enlisted as a Private in Company E, 34th Regiment Ohio Infantry. He was detached from that second unit on 1 Jul 1862 and immediately attached to the 23rd Regiment Ohio Light Artillery. He became a Prisoner of War (POW) on 12 Sep 1862 near Fredericksburg, Maryland and was paroled on that date.

The terms of a parole called for prisoners to give their word of honor not to take up arms against their captors until they were formally exchanged for an enemy captive of equal rank. Parole was supposed to take place within 10 days of capture. Sometimes parolees went home to await notice of their exchange; sometimes they waited near their commands until the paperwork was processed. Although no record has been found, it is assumed that Albert returned to the 23rd shortly after his parole and continued as a member until mustering out at the end of the War.

The 23rd fought at the battle of Antietam on 17 Sep 1862, five days after Albert's parole. It later fought in major battles on 22 Sep 1862; 8 Apr 1864; 9 May 1864 at Cloyd's Mountain, Virginia and 10 May 1864 at New River Bridge, Virginia. The unit was finally mustered out on 10 Jul 1865, at Louisville, Kentucky, in accordance with orders from the War Department.

The family of Albert P. Barnum was enumerated in the 1870 U.S. Census for Ocate, Mora County, New Mexico Territory, where Ramona/Romana was listed under her maiden name. That seems unusual and might possibly be an indication that she and Albert were not yet married on that date. Note, also, that son Albert is shown as having been born in Missouri about 1869, although the Registro de Familia in the family bible lists his birth on 22 Dec 1868 in Golondrinas, New Mexico. Interestingly, the Registro de Familia also shows another child, Samuel Henry Barnum, as being born in Greenfield, Missouri in 1877.

The A. P. Barnum family was enumerated In the 1880 and 1900 U.S. Census for District 23, Mora County, New Mexico Territory. There are a number of unusual aspects to the 1900 census enumeration, suggesting that the information may have been provided by someone not familiar with the exact details. For example: Albert was born in 1843 in Ohio, not 1835 in New York as stated in the census; His father was born in Vermont and his mother in Maine, not New Hampshire and Vermont, respectively, as enumerated; Albert's wife was named Ramona, not Mary; son Charley was born in 1885, not 1886; daughter Mary was born in December 1890, not May 1891; and daughter Francis (should be Frances) was born in July 1893, not in April of that year.

On 29 Jul 1890, Albert P. Barnum filed Civil War Pension Application No. 814.121, in the Territory of New Mexico, stating that he had served as a Private in Company I, 3rd Regiment, Ohio Infantry.

At one time, Albert was known as the "raggedy doctor of Fort Union" in the territory of New Mexico. Supposedly, medical tools once used by him are now on display at the museum at Fort Union, New Mexico. Family history says only that he was a doctor and that he never spoke of his past.

This Barnum line has an interesting history. They married into Hispanic families in New Mexico, along the corridor of Las Vegas, Ocate, La Mesa, Española, etc. That part of the country is rich in Southwest history. The Spaniards that settled there also intermarried with the Pueblo Indians and other tribes indigenous to the area. That may suggest another reason for Albert's short stay in Missouri. In existing photographs Albert's wife, Ramona, looks very much like an Indian and may have been part Indian, part Spanish.

Two of Albert's daughters were midwives and had clinics in New Mexico. They were apparently very independent women. He had ten living children; five boys and five girls. The family is large and widespread. Albert's son, John F. Barnum, had thirteen children, all but one of whom survived to adulthood and had children of their own. It is interesting to note that many of the same given names appear in the Barnum line. Common male names are Samuel, Thomas, John Francis, Charles and Daniel. Those among the females are Laura, Sarah, Emma, Mary and Frances.

Albert P. Barnum may have been trying to hide his past, since he said nothing of his past life and his ancestry has been a 140-year-old mystery until recently. Living family members can remember his relatives coming to visit once. They were said to be "white" (meaning Anglo). Some remember that they were from Kansas, but others said Oklahoma. Both may be correct. While some existing photos of unidentified relatives have printing on the back saying that they were taken in Oklahoma, Albert's older brother Samuel lived most of his life in Kansas.