Built in 1862, the Powder Magazine is a 20-by-20-foot (6.1 m × 6.1 m) brick and stone structure that was used to store gunpowder during the Civil War.

It was originally part of Camp Drum, a facility built upon the outbreak of the American Civil War to address concerns about the loyalty and security of the Los Angeles area.

[2] Phineas Banning, the founder of Wilmington (then known as New San Pedro), wrote to President Lincoln advising that the Union would lose California unless some provision was made to quell pro-Confederacy sentiment.

Camp Drum was built between 1862 and 1863 and was the home base for the California Column, commanded by Colonel James Henry Carleton.

[3] Between 2,000 and 7,000 soldiers were stationed at Camp Drum, and Wilmington became a thriving community with a population greater than Los Angeles during the war.