For more info on this font, read this post.
In 2018, I made a few maps that were inspired by the design of the earliest USGS Topos. While making my own USGS-inspired maps, my search never returned the exact type of font I was looking for. The fruitless search was serendipitous however, because it provided the push to make my own. It was designed for map labels that are no larger than 80-100pt, but usually much smaller. I decided to name it BellTopo Sans with the plan to create a serif version. Currently, I’m getting BellTopo Italic ready, and adding more special characters and glyphs to the sans version. There might be additional tweaks too, so keep looking for those updates!
You may download BellTopo Sans here and use it for free.
BellTopo Sans is under the CC license Attribution-ShareAlike, which means if you download and edit it, you also must do so under that same or a compatible license.