Welcome to the TopoQuest Map Viewer!
Thornton, PA is a populated place located in Delaware County at N39.90733° W75.53159° (NAD83). This is the nearest place in the USGS place names database to the center of the map view below. Look below the map view for a list of other places and locations that are visible within this map view. If you need to locate a landmark or feature, you can search for its location on our Find Places page. If you need to locate a specific USGS topographic map, try our Find Maps page.
Note (5/31/2016) - Want a crosshair at the center coordinates of the map? A number of people have asked, so that option has been added!
Note (6/26/2013) - Map sizes are now larger, and an extra-large (1280x1280) option has been added as well.
Note (8/18/2010) - The transition to the new TopoQuest server is now complete. Aside from a glitch that affected the TopoZone alternative map.asp script much of Monday (8/17/2010) afternoon and evening, all went pretty smoothly. Response time of the TopoQuest website overall should be much snappier, and addition of more 1m satellite / aerial imagery is back underway!
Note (8/2/2010) - Full USGS 1:100K and 1:250K topographic map coverage of the continental US is now completed and online. Plus, I have the new TopoQuest server under construction with a 9TB RAID6 disk array to continue adding satellite/aerial photo coverage. Yay!
Note (7/21/2009) - Locations of places of interest (from the USGS placenames database) within the map area you are viewing are now listed below the map when viewing at 64m/pixel or below. You can click the name of the place to go to its description page, or click the coordinates to recenter your map view on that place.
Note (6/1/2009) - We've started adding 1m/pixel aerial and satellite imagery, starting with Oregon and slowly branching out from there. Please be patient, it takes a very long time to download and process all this imagery, as well as huge amounts of disk space!
Note (3/07/2009) - We've started adding 1:100K and 1:250K scale USGS topographic maps, starting with southern Oregon and moving out from there. Coverage will be a bit sparse at first while we crank up automated processing of map tiles at these topographic map scales. To view 1:100K and 1:250K scale topos, you'll need to manually select them from the sidebar (the Choose Automatically selection will not select these map scales until we have more coverage). You can use the coverage map types to see what areas we've already processed and have online. Also note that satellite photo coverage isn't meant to be particularly useful at this point, it's just (very) experimental.
Note (7/31/2008) - We've started adding 1:50K scale topographic maps of Canada, starting with British Columbia. The Canadian topographic map coverage is still a bit experimental, and integration into the map viewer still needs a little work. The map viewer will not yet automatically select the 1:50K scale topographic maps, so if you're trying to view maps in Canada, you may need to manually switch to the 1:50K Topo Maps selection in the Map Contents section of the sidebar.
Note (4/15/2008) - With the demise of non-subscription access to TopoZone (now merged with Trails.com, a subscription service), we're scrambling to process all topographic maps for the US and make them available as quickly as possible. We now have four Linux PC's crunching map data 24/7 to produce and index map data continuously. We should be adding approximately fifteen 1 degree x 1 degree blocks of map data (approximately 1000 individual 7.5 minute 1:24000 topo maps) per day. We're starting with southern Oregon (because that's where we live!) and northern California and branching out from there.
TopoZone URL Replacement
Do you have a Topozone map URL that you want to convert to the TopoQuest equivalent? Simply replace topozone.com with topoquest.com in the URL, and you'll get the equivalent map as what Topozone used to produce! We have more details on using TopoQuest as a Topozone alternative on our Topozone Replacement page.