The legal age is 16 in the US, although you can get a learner's permit at 14 in Alaska, Arkansas, Iowa, Kansas, North Dakota, and South Dakota. You are not a legal adult until you are 18, so as a parent, you are legally responsible for them until then. As a note, they can only get their license with parental permission, so legal age is only if your parents sign for you. :)
I think it varies by State, yes, but around 16 or 17 is the norm.
Everywhere I have seen it is 16 unless you work on a farm then you can get a farm pass at like 13.
The legal age is 16 in the US, although you can get a learner's permit at 14 in Alaska, Arkansas, Iowa, Kansas, North Dakota, and South Dakota. You are not a legal adult until you are 18, so as a parent, you are legally responsible for them until then. As a note, they can only get their license with parental permission, so legal age is only if your parents sign for you. :)