The New Orleans class of protected cruisers of the United States Navy consisted of two ships which were building for the Brazilian Navy at Elswick, near Newcastle Upon Tyne, England, by Armstrong Whitworth. The Brazilian Navy had ordered four Elswick cruisers, but had already sold the first ship during construction to Chile as Ministro Zenteno. One ship was delivered to Brazil, named Almirante Barroso. The third ship was fitting out as Amazonas, and the fourth was on order as Almirante Abreu.

The 5"/50 caliber gun was the first long barrel 5-inch (127 mm) gun of the United States Navy and was used in the secondary batteries of the early Delaware-class dreadnought battleships, various protected cruisers, and scout cruisers. They were also refitted in the secondary batteries of the armored cruiser New York and the New Orleans-class protected cruisers. They were later used on cargo ships, store ships and unclassified auxiliaries during World War II as well as in emergency coastal defense batteries.