Hello I'm trying to figure out how to shut off the main water valve in this old home I'm renting I think it was built in 1912

Pump or city water? Back to you, Tom

It should be near the street if your in a house or duplex in a hand box. O if your in the city it might be on the side of the unit. Or you would have a house shutoff in the craw space or basement on the side of the house the street is on.

If you're on city water there are two main shutoffs. One's out at the curb in the meter box and the other will be found on the same side of the house, Look for a vertical pipe coming out of the ground and entering your house.
If you're on a pump there should be a shutoff at the pump and another where the water enters your house. Good luck, Tom