The accuracy of all maps depend on the date, scale, and purpose. I've found many topographical maps to be very accurate when it comes to track arrangements, and some not so much. It depends on the area in question and one has to remember that maps are just a snapshot in time. In the areas that I've researched, USGS 1:24,000 scale topographical maps typically don't show all of the tracks in a yard but industrial spur accuracy is pretty good. I normally use the USGS maps in conjunction with Google aerial/satellite photos and other historical ground level and aerial photos if available.

For example, the siding arrangement in a nearby village was shown accurately on a topo map even though it couldn't quite be made out from an aerial photo from the approximate same time frame. Growing up in the area, I didn't recall a passing siding at this location either, only an industry track. Years later I found a C&NW track chart that also showed the passing track, confirming what was indicated on the topo map.

This 1955 aerial photo shows an industrial siding on the north side of the mainline, serving an elevator and other agriculture-related customers, but it's not really possible to make out a siding on the south side of the main.

This snippet from a 1964 USGS map does show the siding on the south side of the mainline. It also shows the location of the depot (that small black rectangle between the industrial siding and the mainline) that matches the aerial photo.

This is from the 1959 track chart that verifies the siding on the south side of the mainline.

There is one difference between the map and chart: the arrangement of the two switches on the west end. It's certainly possible that the passing siding west switch was moved further to the east after the 1959 track diagram was published but before the 1964 map was developed, or it could be something that was missed when the map was field checked.

So in my opinion, USGS topo maps CAN be a very handy source for track arrangements. While I would not rely on them exclusively, especially in the absence of railroad engineering documents, they can be combined with photos and Sanborn maps to produce a good image of a railroad's physical plant in certain areas. To write them off as "not accurate at all as far as track arrangements" is to miss out on a lot of historically correct information.

Here is an example of the difference between USGS Topo Maps, Sanborn Maps and railroad engineering maps.

This is the USGS Topo Map of the IC freight house area in Centralia, IL:

Here is a Sanborn Map of the same area (note the Sanborn Map sheet only covers the area by the freight house and doesn't show the tracks to the west which are on a different sheet:

As you can see the Sanborn Map shows the 4 tracks at the freight house and the team track including the spur that serves the boiler plant.  Those details are missing from the USGS map.

And here is an IC property map of the same area:

I am currently modeling this area on my layout.  The topo map gives me the actual terrain.  Without it I wouldn't have known about the embankment (about 5 feet) that is behind Midwest Dairy and WA Glore Lumber (Marked as Mill on the IC Map).  It's no longer there as the area has been leveled but it was there in 1955 which is the era I model.

The Sanborn Map gives me details about buildings that are no longer there.  Only Kohl and Meyer wholesale grocery is still there and it is now home to the Centralia Area Historical Society.

The IC property map gives me the details of the track layout.  As you can see, the tracks, specifically the location of the switches look different on the IC map then they do on the Sanborn map and some of them aren't even marked on the topo map. 

You can't get everything you need to model a specific location, especially if you are modeling it as it was 60 years ago without all three sources.

Jeff White

Alma, IL

It appears that the era of a topo map has something to do with its accuracy.  Maps made in the decade from 1949-1959 appear to be more accurate than maps made both earlier and later.  By the 1970's most railroads are shown as a single line whereas in earlier decades they tend to be more accurate as in Tom's map above.  Much older maps like 1910-1930 sometimes appear too complicated and are not drawn cleanly.

Historic Aerials is a very useful tool in obtaining topo maps from different years and determining what remains today.  On the other hand aerial photos are not very useful until post WW II and then it seems to depend on location.

The Sanborn maps are really a great addition but many small towns were never mapped and larger cities that had industry outside the city limits were not mapped.

"You gotta know the territory."

Robert

Not saying not to use any source.  In the words of Reagan, "Trust then verify."  I have also found railroad maps to be "wrong" especially ones more than a decade from another source.  One of my jobs as a trainmaster was to identify tracks we could retire.  A map drawn of my territory in 1980 would not be accurate for 1990.  Sanborn maps can also be confusing as to the owners of property.  The owner listed may be the owner, but not the "operator".  I have found instances where an owner of a property leased it to another company, so all the photos showed it as the ABC company, but the Sanborn map showed it as XYZ company.  Or properties were sold or went out of business.

A friend knew a surveyor that used "stations" (surveying, not railroad) on the tracks of a railroad on the boundary of a property.  Then he came back a month later and all his surveys were off.  He didn't realize they ran a tamping gang over those tracks and moved the tracks over 6-8 inches and raised it 4-6 inches.

The more info you can get the more you will understand what happened.    

I found a drawing of Birdsboro, PA done in 1890 and it showed an engine house, but no railroad drawing or Sanborn map (1895, 1900, 1903) I have seen  showed it being there.  So which one is right?  Then I found the corporate annual reports for the railroad and they mentioned the engine house blew down in a blizzard in 1893, so actually all of them were right.

@jwhite & dssa1051 - agreed 100%!

It's interesting to watch the rail system (and other industrial infrastructure) expand and contract over the years. I mostly follow the C&NW and M&StL and those systems have grown and then shrunk considerably over the past 100 - 125 years. Some of the areas where those companies operated, mostly in South Dakota, weren't even mapped that long ago by the USGS so I've had to work with the snippets available on Sanborn maps, library archives, etc...

Also, while the 1:24,000 maps aren't always 100% correct as to track arrangements, I do find them close enough especially since like many modelers, I don't have enough physical space to reproduce a prototype location exactly.

It's good to see others know about these resources as well!

The key to using maps is to use the information they best provide. USGS maps are good for grades and elevations. Sanborn maps or good for different industries, business, and houses. Railroad valuation maps are good for track structures and railroad buildings.  Use the information of various maps  to create a better picture of what was there. 

Use the information from them to build a composite for your layout.  

It's interesting to watch the rail system (and other industrial infrastructure) expand and contract over the years.

​One fellow I worked with started in the signal department.  His first job was helping install signals on the MP Wynne Sub and about 5 years later his last job in the signal dept. (he changed departments) was removing the signals on the Wynne Sub.

Also, while the 1:24,000 maps aren't always 100% correct as to track arrangements, I do find them close enough especially since like many modelers, I don't have enough physical space to reproduce a prototype location exactly.

​I have found Google Maps (or equivalent) to be very helpful in locating stuff.  Even long retired branch lines.  Often you can still find a scar in the tree line where the right of way was.  I located a wye on a branch that I didn't know was there that way.   You can even see the types and number of cars at industries.

​www.historicaerials.com is also a great resource.  If you can find an older aerial, you can see the number of cars at industries or yards to get a feel for how busy the locations are.

The University of Minnesota has a good collection of aerial photographs dating back to the 1920's that are free for downloading.

https://www.lib.umn.edu/apps/mhapo/

The photos cover most of the state and some boundary areas of the Dakotas, Iowa, Wisconsin, Ontario, and Manitoba. Unfortunately I've not been able to find a similar source for other states.

In no particular order but I find the following to be very useful. 

Track charts. sometimes will require a lot of digging to find the right ones.

www.historicaerials.com Recently been pointed to this site. Some images are very low resolution, but the site offers some neat tools to show the difference in years of a location.

Sandborn Maps. As has been pointed out. Good source of info if you can find the right one, but the maps are not always 100% accurate but will get you in the right ball park.

Postcards... yes I know but if you dig around you will sometimes find a gem.

Google Earth/Maps. Very important if modeling a present day line. As Dave has pointed out. If you can get yourself to the right location you can see a lot with the images that google maps offers.

Internet searches and Historical Society forums. Not always Railroad related. look at City Societies also.