How do I add a Zip Code Search on a website

I am creating a website that lists several band's events across the US. The original plan was to show all the events in each state. How can I add a zip code search to show the upcoming events in that area? For example, if you enter 90210, and choose "within 10 miles" or "within 30 miles", etc, it will show the events within the chosen mile radius. I am assuming I will need a database of the zip codes? Any help would be appreciated!