This is a good question and I'm no map scholar. Cartotalk may have some answers but I'm not sure if they would discuss things like we do here. Just brainstorming I would think that technology was important...railroads, telegraphs, electricity, photography, etc meant that people could travel around much faster and thus map things faster. The printing brought maps to the masses and this probably inspired many folks to buy some survey equipment and do some scouting in the American west...much like the Gold Rush. When the gold ran out they found silver in the Comstock Lode and others went looking for other precious metals like copper and nickel. So, greed was a factor and that's not new but it did speed things up. Barbed wire fences were invented back then and that would have been important for the land grab to stake out your land...once others start staking out their land then you need more surveying and more accurate maps. With Indians all over it would be nice to know where they lived so one could avoid problems. This was also the time of England's empire and they would certainly need good maps. There was a lot of adventure and exploration in this time period - the American West (pretty much everything west of the Appalachians to which Lewis and Clark found the route to the west coast), South America and the Amazon, the race to the poles, finding the northwest passage north of Canada, whaling, the Dark Continent of Africa, etc.