Are the arches in one or two states?

There is only 1 Arch and it is in 1 state, St Louis MO.

Its in Missouri its one masive arch

It's one arch and both "legs" of it are in Missouri.

Don't confuse this with the golden arches. This is the real thing and it is only in Missouri.

They are both in Missouri.

I used to think it spanned the river but no, just in Missouri.

Is in Missouri

That would be cool if it went across the river

In Missouri by the Mississippi river it pretty nice place to see

There is only one arch!