Whether you need to make a call or trace a number, you can locate a pay phone online. There are numerous online databases containing the locations and numbers to pay phones all over the country and some have information for other countries.
Check out The Payphone Project. This website started as a joke but has grown into a substantial database of about 500,000 pay phones across the United States. You can search by a phone number and, if the number is in the database, it will list the address, city and Postcode of the phone. You can search by city and get a list of all the pay phones, along with their address and Postcode. However, if you type in a city's name, such as San Francisco, you may find a phone at a bar named the "San Francisco Saloon" that is actually in Chicago. The best thing about this site is it is free.
Try the Payphone Directory. The best thing about this site is that it has pay phones from several countries, including the United States, Canada, Germany and the United Kingdom. It is also free. However, there is no number search feature on this website. This means it is great for finding a phone in a particular country or city, but if you need to trace a phone number, you are out of luck.
Go to Public People Finder. This service has a feature in which you can search for a pay phone by its phone number. On the plus side, it has the largest searchable database of these three options, so it is likely to get results. However, as of 2010, the fee for this service is £57. To purchase the service, go to the website and press "Order." You will need to provide a phone number and click "Search." The site will search its database and usually come up with a location in one to three days. The location of the phone will be provided via e-mail.