Looking for half sister, help appreciated?

recently found out i have a half sister.

i was brought up by my grandparents

my family has kept information about the half sister away from me.

so far i found a first name, the mom's name kinda sketchy working with variations of spelling.

i believe i know her birth state and she moved to my state for a while.

i know the exact day and month but the year i have narrowed to within 3.

i dont know if she's still here.

or alive.

i have a paper with a street address, no city or state of where she lived about 30 years ago.

with this info, what free website can i visit to find out more?