An easy way to find out what county a town is in is to use a free tool on mapdevelopers.com. As of November 2015, the tool will allow you to discover the county you are currently in based on location, or you can manually enter an address.
On mapdevelopers.com, click on the "Additional Maps" tab to make a dropdown menu appear. Click "What county am I in?" Once the page loads, click "Find what county I'm in" and your browser will ask if you want the site to access your location information. Click "OK" and the site will list your county under the header "This is the address information closest to your current location."
To manually search for what county a town is in, enter an address into the "Enter Address" search box and click "Find County of Address." In addition to revealing the name of the county, the site will show a map of address you entered, the ZIP code, the latitude, and the longitude.
Double-clicking anywhere on the map will reveal the name of the county in the location you clicked. You can also use the site to share your location by copying-and-pasting the generated URL in the box under the "Share your current location by sending this link" header.