I got a 1985 Bonneville that runs great. Lately I noticed it started making a squeaking sound. It usually does it when I hit the breaks and turn (mostly when I turn left). I opened my door while driving to listen to where it'* coming from. It sounds like it'* right under the drivers side front. I think it'* in the front wheel. I'm thinking it may be the breaks going out but I"m not sure. Any help would be appreciated. Thanks.

Chances are its Brakes. Those would be my first point of Inspection.
Generally, the inside pad will wear out faster on most cars, take a good look at that one
That caliper could be haning up as well, hence one side doing it and the other side not.