In April 1941, eight months before the attack on Pearl Harbor, construction began at Rock Island Arsenal on what would become the world's largest ordnance storehouse, Building 299. The building enclosed 18 acres under one roof, with space enough for 17 football fields inside. It was equipped with rail tracks and could load and unload a complete train at its interior docks. Building 299 was built to accommodate the business generated by America's new role as an "Arsenal of Democracy" for those nations under attack by the Axis Powers.


As American production continued to escalate in the years leading up to the nation's entry into World War II, Rock Island Arsenal saw a steady increase in depot activities. By 1940, it was deemed that the interior storage available in Storehouse W1 (now Building 350) was inadequate. While RIA had possession of Savanna Proving Grounds in Savanna, Illinois, the storage available there was outdoors, and the nature of war materiel being produced required onsite indoor storage space.

It was therefore deemed necessary to construct a larger space for storage and loading. In 1941, construction began on Building 299 with the intention of providing space to store war materiel and load that materiel onto freight trains. The covered space allowed better productivity, faster loading, and increased security. Building 299 was served by two railways.

After the war ended, Rock Island Arsenal once again became a central storage point for overflow parts, equipment, machinery, and weapons. Both the satellite site at Savanna and the storage space on Rock Island were used for this purpose. Building 299 served as the main indoor storage facility for many items that were returning from Europe, and run-over machinery that was used for production at the Arsenal itself.

Today, Building 299 functions in much of the same way as it did following World War II: As a storage facility. The space is complemented by a large outdoor storage space to the east.