It's a fake map.
The inset map on the lower right seems to correspond reasonably well to the map at http://www.cprr.org/Museum/Maps/_cprr_map.html .
It's very hard to tell exactly where the larger part of the movie map is supposed to be, but the sierra nevada mountains are in CA, and so the part of the map that must match must be in CA. https://en.wikipedia.org/wiki/Sierra_Nevada_(U.S.)
The train tracks on the movie map show a three way intersection of the trans pacific railroad - east, west, and south. There are only three such junctions near the sierra nevada mountains, as shown on the map first linked. One near Stockton and one near Sacramento, and one near Rocklin.
Sacramento has the American river running east-west above/through the city, but almost all rivers on the movie map run north-south, and those tributaries that run east-west are south of the railroad intersection on the movie map - Sacramento appears to be directly on the intersection in the second link, putting the river north of the intersection. River placement results in a non-match.
Rockton has the opposite problem. Zoom in too far, and there are no rivers. Zoom out far enough to get mountains and the movie map is missing Folsom lake. It can't be Rockton.
Stockton has a mess of lakes and rivers to the northwest, which are all in view if you zoom out far enough to see the Sierra Nevada mountains (on the movie map). The real life lakes to the northwest aren't shown on the movie map. It can't be stockton.
That rules out all three locations.
Therefore, assuming the movie map accurately shows the trans pacific railroad junctions and that the bodies of water have not substantially changed, then no, it's not real. Of course, the movie makers may have taken any map, overlaid fake railroads on existing geographic features, but I'd argue that such a map would be equally fake as the railroad is one of the most important landmarks of the time.
 it seems only fair to assume that major geographic references like the sierra nevada mountains, California itself, and the direction of north must be required elements of a match to the movie's Hill Valley location. Otherwise we would have the unreasonable task of evaluating every mountain range in every country from every angle and every level of zoom. I also assume some semblance of scale, such as not allowing bride's pond to be as large as a great lake when it's named 'pond'