The Secretary of the Navy is in charge of naming US Navy ships, under the direction of the president and with the guidance of Congress.
But it’s not just a random choice; there have long been rules and traditions concerning how ships are named.
On Monday, the Congressional Research Service released a report on the current rules for naming ships recently obtained by the Navy and those that will be procured in the future. The report outlines the rules for naming ships for Congress, but the ultimate decision rests with the Secretary of the Navy, so of course there are exceptions.
In fact, the report says exceptions to the naming rules are as much a Navy tradition as the naming rules themselves.
Learn about the Navy’s ship-naming rules — and the exceptions — below.
An artist rendering of the future Columbia-class ballistic missile submarines.
US Navy / DVIDS
The Columbia-class ballistic missile submarines will replace the Ohio-class, starting to patrol in 2031. The first submarine has been named Columbia for the District of Columbia, but the Navy hasn’t publicly stated what the rule for naming this submarine class will be.
The 12 submarines of the Columbia class are a shipbuilding priority. The Columbia-class Program Executive Office is on track to begin construction with USS Columbia (SSBN 826) in fiscal year 2021, deliver in fiscal year 2028, and on patrol in 2031.
The Seawolf-class fast-attack submarine USS Connecticut moored at US Fleet Activities Yokosuka for a port visit.
Petty Officer 1st Class Benjamin Dobbs / US Navy / DVIDS
The Navy doesn’t seem to have a rule for naming Seawolf-class attack submarines. The three submarines of this class still in service are the Seawolf, the Connecticut, and the Jimmy Carter — named for a fish, a state, and a president.
Designed to be the world’s quietest submarines, Seawolf-class submarines are one of the Navy’s most advanced undersea warfighting platforms, and unique among US submarines.
The Jimmy Carter now serves the same secretive purpose as the USS Parche, the US Navy’s most decorated warship.
The Virginia-class fast attack sub USS Hawaii sails by the battleship Missouri Memorial and the USS Arizona Memorial while pulling into Joint Base Pearl Harbor-Hickam, June 6, 2019.
Mass Communication Specialist 2nd Class Charles Oki / US Navy / DVIDS
The Nimitz-class aircraft carrier USS Carl Vinson (CVN 70) underway in the Indian Ocean prior to flight operations. The Carl Vinson Strike Group is currently on deployment to promote peace and stability and respond to emergent events overseas. USS Carl Vinson will end its deployment with a homeport shift to Norfolk, Va., and will conduct a three-year refuel and complex overhaul.
U.S. Navy photo by Photographer’s Mate 3rd Class Dusty Howell
USS Preble, USS Halsey, and USS Sampson underway behind the aircraft carrier USS Theodore Roosevelt in the Persian Gulf, March 24, 2018.
The Independence-variant littoral combat ship USS Montgomery at Changi Naval Base in Singapore.
Mass Communication Specialist 2nd Class Tristin Barth / US Navy / DVIDS
USS Boxer (LHD 4) prepares to launch Australian S-70A Blackhawks during flight operations in support of Exercise Talisman Saber 2005.
U.S. Navy photo by Photographer’s Mate 3rd Class James F. Bartels
The amphibious transport dock ships USS San Antonio and USS New York underway together in the Atlantic Ocean off the coast of Virginia, June 9, 2011.
A graphic representation of a future U.S. Military Sealift Command John Lewis-class oiler.
U.S. Navy photo by Mass Communication Specialist 1st Class Armando Gonzales
John Lewis-class oilers will be named for civil-rights and human-rights activists, like Lewis himself.
Some of the Navy’s Lewis and Clark-class dry cargo and ammunition ships are named for civil-rights leaders, like Cesar Chavez, too, although the rule is to name them for explorers.
Lewis, who fought for civil rights alongside Dr. Martin Luther King and is now a member of Congress, attended the keel-laying of his namesake oiler earlier this year.
The Spearhead-class expeditionary fast transport ship USNS Carson City arrives in Sekondi, Ghana, in support of its Africa Partnership Station deployment, July 21, 2019.
John McAninley / US Navy / DVIDS
USNS John Glenn underway off the California coast, January 9, 2014
An artist rendering of the future USNS Navajo (T-TATS 6), February 15, 2019.
US Navy photo illustration
This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.