The U.S. Navy adopted the Maxim-Nordenfelt 37 mm 1-pounder as the 1-pounder Mark 6 before the 1898 Spanish–American War.
The Mark 7, 9, 14, and 15 weapons were similar.
It was the first dedicated anti-aircraft (AA) gun adopted by the US Navy, specified as such on the Sampson-class destroyers launched in 1916-17.
It was deployed on various types of ships during the US participation in World War I, although it was replaced as the standard AA gun on new destroyers by the 3 inch (76 mm)/23 caliber gun.

Previously, with the advent of the steel-hulled "New Navy" in 1884, some ships were equipped with the 1-pounder Hotchkiss revolving cannon.

In the aftermath of the Battle of Blair Mountain, the United States Army deployed artillery, including pompoms:  "Their armament was strengthened with a howitzer and two pompoms."

Rapid-firing (single shot, similar to non-automatic QF guns) 1-pounders were also used, including the Sponsell gun and eight other marks; the Mark 10 to be mounted on aircraft.
Designs included Hotchkiss and Driggs-Schroeder.
A semi-automatic weapon and a line throwing version were also adopted.
Semi-automatic in this case meant a weapon in which the breech was opened and cartridge ejected automatically after firing, ready for manual loading of the next round.

It is often difficult to determine from references whether "1-pounder RF" refers to single-shot, revolving cannon, or Maxim-Nordenfelt weapons.
The U.S. Navy adopted the Maxim-Nordenfelt 37 mm 1-pounder as the 1-pounder Mark 6 before the 1898 Spanish–American War. The Mark 7, 9, 14, and 15 weapons were similar. It was the first dedicated anti-aircraft (AA) gun adopted by the US Navy, specified as such on the Sampson-class destroyers launched in 1916-17. It was deployed on various types of ships during the US participation in World War I, although it was replaced as the standard AA gun on new destroyers by the 3 inch (76 mm)/23 caliber gun.
Previously, with the advent of the steel-hulled "New Navy" in 1884, some ships were equipped with the 1-pounder Hotchkiss revolving cannon.
In the aftermath of the Battle of Blair Mountain, the United States Army deployed artillery, including pompoms:  "Their armament was strengthened with a howitzer and two pompoms."
Rapid-firing (single shot, similar to non-automatic QF guns) 1-pounders were also used, including the Sponsell gun and eight other marks; the Mark 10 to be mounted on aircraft. Designs included Hotchkiss and Driggs-Schroeder. A semi-automatic weapon and a line throwing version were also adopted. Semi-automatic in this case meant a weapon in which the breech was opened and cartridge ejected automatically after firing, ready for manual loading of the next round.
It is often difficult to determine from references whether "1-pounder RF" refers to single-shot, revolving cannon, or Maxim-Nordenfelt weapons.
QF 1-pounder pom-pom