The best way to find out what congressional district you are in is to go to your state's district locator page and search for your address, city or zip code. You can do this by going to your state's official government page and searching for the district locator or by using a search engine to directly locate your state's district locator page
Congressional districts change every 10 years to reflect the number of people in the area, as recorded by the U.S. census. For this reason, there is no way to make a comprehensive listing of what county, township or city is located in each district. This can make finding your district a bit more complicated than finding some other information.
Fortunately, a state's official government page features a district locator page where you can search for your location. It is strongly recommended that you search by your zip code and state, rather than simply your city, because the nature of congressional districts means that your city, especially if it is a heavily populated one, may be divided up into multiple districts. Your state's district locator page may offer information besides congressional districts, so be sure to read all directions and map legends carefully and thoroughly.