The opening and closing times of polling sites vary by state. The closing time indicates the time by which you must be in line in order to vote – not the time by which you must have voted.
For example if the time the poll closes is 7:00 p.m. and you are in line at 7:00 p.m. you must be allowed to vote. You can go to your state's website to find the polling hours. You can get the web address in the Election Official Directory. Choose your state and region to find the link to your Local Elections Website and also find the contact and address of your local election official.