JOSEPH HENRY LEONHARDT was born on July 1, 1894 in Camden, New Jersey to Charles Leonhardt and his wife, the former Mary Moore. The 1900 Census shows him living with his parents and older brother Frank at 553 Division Street. His father worked as a machinist and the Leonhardt's owned their home. Sadly, on May 22, 1907 Charles Leonhardt passed away. The Leonhardt's were still at the Division Street address when the Census was taken in 1910. Michael Moore, Joseph Leonhardt's 85 year-old maternal grandfather was also living with them.

On October 20, 1914 Joseph H. Leonhardt married Margaret Eva Keenan. A son, Charles Leonhardt, was born in May of 1915, followed quickly by a daughter, Margaret Mary in October of 1916. When he registered for the draft on June 5, 1917 he was working at the New York Shipbuilding Corporation shipyards and living at 1421 Norris Street. On May 8, 1919 his wife gave birth to a daughter, Anita. The 1920 Census shows the Joseph Leonhardt family, his mother and brother Frank all living at 553 Division Street. Both of the brothers were working as shipfitters. In December of 1924 another daughter, Mary V. Leonhardt, was born. The 1930 Census shows Joseph Leonhardt and his family at 514 Division Street. The moved back to 553 Division Street by the fall of 1932. On April 9, 1931 Joseph Leonhardt's mother, Mary Moore Leonhardt, passed away. On November 14, 1932 his wife, Margaret Eva died.

Joseph Leonhardt was appointed to the Camden Police Department on April 15, 1924. He was promoted to Detective in the summer of 1934 and almost immediately was thrown into the center of controversy. He was with Detective William T. Feitz on September 2, 1934 when Feitz walked into a hold-up at a disorderly house at 243 Sycamore Street and was shot to death. A probe of in the wake of the killing yielded indictments against six Camden police officers, including Joseph Leonhardt. He and four others were acquitted on April 1, 1935. He was reinstated on June 29, 1935 and returned to duty with the Camden Police Department a few days later.

Charles Leonhardt married Sarah Murphy and Anita Leonhardt married George Peyton. Late in 1939 Joseph Leonhardt retired on pension from the Camden Police Department. The 1940 Census shows Joseph Leonhardt, his brother Frank, son Charles and his wife, and daughters Margaret and Mary all at 553 Division Street. Joseph Leonhardt died May 8, 1941 and was buried at Calvary Cemetery.