Master Legend/Key for Early 20th C. USGS Topographic Maps

Is anyone aware of a general legend or key that was published describing the symbols used on USGS topo maps from around 1909 - 1920ish? I know that the symbols are fairly standard, but the earliest master key I can find appears to date from c. 1970s. Some maps have a limited key on them, and some do not. I’m particularly looking for information about how roads were described.
I’m researching this at work, and it’s so easy to get sucked down the rabbit hole looking at these older maps…

The National Map has some historic USGS topos available online. Do you know a location and size/scale?

This is a pretty cool topic. I think there were multiple agencies working on maps at the time. I looked at a 1893 1:125000 map from around the 40th parallel in Kansas and it had no roads shown just railroads. I looked at 3 maps from 1902 to 1906 and they pretty much just show 2 parallel tracks with solid lines or dashed lines. I’m assuming main roads and secondary rural roads (certainly not paved vs. dirt). By 1944 they have a full legend on the map with 6 different road classifications from “Hard Surface, heavy duty, more than 2 lanes wide” to “Dirt Road” or “Railroad in Street”

I found a Sardinia Ohio 1:62500 (why?) with 4 types: Parallel lines with one slightly heavier (main road?), parallel lines with the same thickness (well used?), parallel dashed (wagon trail :), parallel with perpendicular dashed, (railroad and road). None of the maps from that era have legends.

Primarily, these are southern Illinois - Gallatin County in particular, but we’ve been looking at some other counties in southern Illinois as well.

I did a Google Books search on the terms “conventional signs” and “geological survey”. Among other leads, I found a book from 1913 called Topographic Instructions of the United States Geological Survey. Starting on page 206 there is a long list of symbols and their meanings.

I’m not sure what you are looking for, but here are some resources I use.

Historic Aerials has actual aerial photos of that area (like Google but B/W) back to 1938 and topos to 1906:


A scale of 1:62,500 is common in the metric system. But I’m surprised an early map in America would use it.
A scale of 1:63,360 means one inch equals one mile.

This website explains: Map Scales

Basically, 1:62500 is easier to work with than 1:63360; it scales up more easily. The equivalent scale for the 4º maps is 1:1,000,000. Note that the 7.5’ quads use the even easier 1:24000, which is not scaled at all from either the correct or the modified 1" = 1 mi.

I read the explanation and I still don’t get the decision. It seems like a stupid place to allocate your error. I’d much rather the actual MD to GD scale be correct than to have a 30’ quad compare to a 15’, especially with longitudinal scale constantly changing.

I’m sure they did it for a reason, just seems odd.

As far as 1:24000. I assume at some point they had to switch to something divisible by 12 to make the inch to foot conversion easier in a time before calculators.

I think the key thing involved is not the fact that 15’ quads are 1:62,500, but rather that 4º quads are 1:1,000,000, and everything is sized down from that. In actuality, the 4º quad should be at 1:1,013,760, which, if you think of it, is pretty silly. The difference is about 1/73rd of an inch which is essentially unnoticeable.