Lewis G. Arnold was born in Perth Amboy, New Jersey and graduated from West Point in 1837, placing tenth in his class.

After the war, he once again commanded troops in Florida, and led a detachment against the Seminole Indians in the April 1856 Battle of Big Cypress.

[2] At the onset of the Civil War, he was promoted to major of the 2nd United States Artillery and was assigned to Fort Jefferson at Dry Tortugas, Florida, in January 1861, leaving his command at Fort Independence, Massachusetts.

In January 1862, he was promoted to brigadier general, and in October 1862 was transferred to command the city of New Orleans after it fell to Union forces.

Arnold died 8 years later in Boston, Massachusetts and is buried in St. Mary's Episcopal Church Cemetery in Newton Lower Falls.