I am assuming you are inquiring about drinking age
some places in Canada its either 18 or 19.
but I heard it was 21 years old.
It is the same age almost everywhere in the US to serve alcohol which is 18. There are one or two states that have higher ages, but im not sure which ones. Waiting table you should be able to serve alcohol, but being a bartender is usually 21.
you have to be 21 in the us to serve alcohol