It might seem archaic these days, but at one time the canal researcher would reach for their paper topographic map instead of clicking on Google Earth. Many of us still have our venerable paper maps with notes in the margins and circles around important sites. Even with Lidar and Maps and Google Earth, the old topographic maps are a valuable record of what once was. But do you know about the USGS topoView website which can offer decades of maps with a couple clicks?
Before we get to that, just be aware that the topographic mapping process began in 1880s and proceeded across the country over the decades. This is the one limitation to using these maps in canal research as the canal might have been long gone by the time the first map was created. But simply seeing the contour of the land might help to understand the why and how of a canal route.
The United States Geological Survey, or USGS, offers topo maps that cover the United States, online and for free, by way of their topoView website. Once in the site, you will be presented with a larger general purpose map where you can zoom in to quickly find the state, city, river, road, or feature. With a click on the map, a dashboard will open presenting a list of the available maps for whatever quadrant you happened to select.
The red circle on top left will show the number of available maps for that quadrant. The date range slider will allow you to chose the date if you want to focus on a certain time. Below that are a number of colored circles with the 250k, 100k, and so on. These are the scales available just in case you only want to see a certain type of map. If you click on a map scale, the number in the red circle will change as will the listing, showing what is available.
The listing of maps, from oldest to newest, will show you the quadrant name, the date of survey and scale. By clicking on the SHOW button (in this example, I have clicked on it so it now appears as a HIDE button), the map will appear and you can happily move around the page, zooming in or out, and moving with a simple drag of the mouse. There is also a MAP TRANSPARENCY slider that allows you to move back and forth between the general use map and the topo map. This is very handy if you happen to be trying to find a feature that you know about and want to see what used to be there. There are also helpful videos on YouTube if you really wish to dive into the mapping, but for general use, navigation around the site is easy.
Maps can be downloaded in a variety of formats that include JPEG, KMZ, GeoTiff, and GeoPDF. These are all free. These will be delivered to your computer as a ZIP file. You can click on the EXTRACT button to open the map and then you can save it as you wish.
Older maps use a scale that is 1:63,360, where one inch equals one mile. This scale presents canals as a blue line without much detail. If you happen to get lucky, locks might be represented with a V mark, but in most cases, you will need to look for the contour lines to try to find lock sites. You can quickly change maps by using the list on the right side of the page to scroll through what is available. As you progress through the years, you might find a change in scale as newer maps were made in 1:24000, where one inch equals 2000 feet, or slightly less than a half mile. At this scale, you might find canal remains as seen in the 1954 map of Schenectady. The quality of the maps can vary, so it pays to click on all the maps to see how they change over the years.
As you can see here, most of the older maps are in the larger one inch to a mile scale. Once you have downloaded the maps to your computer, you can do as you wish with them. You can use any photo editor on them as you have them as JPEG files. Here is one that I used in a prior post where I stitched two together.
So have fun, and let us know if there is some technique or way to use that I missed.