What happened is that you have a gate valve, and have experienced a fairly common problem in that the gate snapped when you turned it off. Now the gate won't come up when you turn the stem.
An emergency fix to this : try two things:
(a)Turn the handle several turns counter clockwise to be sure the stem is up. Now, rap the valve body firmly, several times, with a hammer. Give it a good smack, but not like you are trying to put one over the wall at Fenway.
(b) If that doesn't work, get the city to come out and turn off their stop. Unscrew the bonnet assembly of your valve. Then try to grab the gate with a pair of needle nose. Now put the bonnet back on, and you will have water. It is not prudent to NOT have a main shutoff, so you want to replace that valve as soon as possible.