Oscar Herman Rehmann was born on July 3, 1898 in Atlantic County, New Jersey. He was the son of Julius C., Sr. and Rosie (Menger) Rehmann.

In the 1900 census, he was living with his parents and siblings at 115 Egg Harbor Road, Hammonton, Atlantic County, New Jersey. In 1910, they were living at a farm at 720 Twelfth Street in Hammonton and by 1918, he was a sheet metal worker assistant at Atlantic Loading Company in Elwood, NJ.

Circa 1920 he married Mary who was born about 1902 in Pennsylvania.

In 1920, he was still on Twelfth Street and was a "stationary fireman" and then a laborer doing odd jobs in 1930. The 1940 census has him living in the same place and working as a foreman for the W.P.A (Works Progress Administration) at an annual salary of $492.