How many US cities are in more than one state? (not different cities with the same name, but cities that straddle a state border)

This question does not have an absolute answer because there are always problems in defining the limits of cities.

The metropolitan area of New York City covers parts of New Jersey. (and possibly Connecticut if you cast your net wide enough), but the Jersey suburbs are not officially part of NYC. Similarly, Washington extends into Virginia and Maryland and greater St Louis extends across the Mississippi from Missouri into Illinois. I’m not sure how far the outer suburbs are considered part of the main city in either case. I note that the postal address of the Pentagon is in Washington, DC, although geographically I believe it’s in Arlington, VA.

Kansas City is a traditionally accepted answer to this question, as it clearly spans both Kansas and Missouri.

The Kansas City metropolitan area is a bi-state metropolitan area. ... The larger Kansas City Metropolitan Area as seen on a map can be visualized roughly as four quadrants:
The southeast quadrant includes Kansas City, Missouri, and surrounding areas in Missouri. It includes the notorious Grandview Triangle.
The southwest quadrant includes all of Johnson County, Kansas, which includes the towns in the area known as Shawnee Mission, Kansas. Interstate 35 runs diagonally through Johnson County, Kansas, from the southwest to downtown Kansas City, Missouri.

https://en.wikipedia.org/wiki/Kansas_City_metropolitan_area

This website lists other towns that are considered "border towns/cities" -- i.e. towns that may be considered as valid for this question. Whether or not these count depends on your definition of "city" and how close / what parts of each city cross into another state. In some places a town takes on a new name when it crosses a border. So it it now two different towns?

Here are the candidates:

https://en.wikipedia.org/wiki/Border_town#United_States_within

[ This top question has been modified heavily by Terry, as it is a frequently asked question ]

According to a few sites I found, Kansas City is the only city that exists in two states, but I can name another (though far smaller) city that straddles a border: Bluefield, West Virginia/Bluefield, Virginia.

It's also worth pointing out that the metropolitan areas of more than one large city include parts of more than one state. This can be said, for example, of both New York City and Chicago.

https://en.wikipedia.org/wiki/Bluefield,_West_Virginia

Bristol Tn/Va

http://bristoltn.org

or

http://bristolva.org

Does Texarkana count?

Lake Tahoe/stateline Cal/nevada

Actually I think Kansas City, MO and Kansas City, KS are two different cities.

Even if a city straddles a border and shares a name, they have to be 2 different cities because they are governed by 2 different sets of state laws.

Washington, DC wouldn't be an example for this question. The District of Columbia was originally 10 miles square and included part of what is now Virginia across the Potomac River. That part was given back to Virginia and is mostly Arlington today. None of the city of Washington or the District of Columbia is on the Virginia side of the Potomac now. The city limits on the Maryland side are quite definite, making up what remains of the 10 square miles. The surrounding area of Maryland and Virginia may all be considered the "Washington metropolitan area" but once you are outside of the city limits, you are in Maryland, in separate communities like Chevy Chase, Bladensburg, or Capitol Heights. They all have their own Mayors and city councils. And once across the river, you are in Virginia. The Pentagon has a Washington address because it is a Federal building, however it is located entirely in Virginia.

Worldatlas.com lists four cities:

Bristol (Virginia and Tennessee)
Texarkana (Arkansas and Texas)
Texhoma (Oklahoma and Texas)
Union City (Indiana and Ohio)

https://www.worldatlas.com/articles/cities-in-two-states.html