It all depends on what kind of topographic maps you are looking for. If you are looking at purchasing maps for your particular State and know that you will need more than just a few maps you will be much better off to go to National Geographic and purchase the whole set of maps for your particular State. I have the map program for the State of Missouri and it is fantastic. You will get the most up to date topographic maps of the entire State. You must remember that most topographic maps that you will purchase, or get on a map program can be quite old. If you go somewhere and purchase the maps you will see on the lower right corner the date of the map. In many instances these maps are twenty to thirty years old, and these are sold as new maps.
A few years ago the Missouri Department of Natural Resources in Rolla, Mo. decided to get rid of its smaller maps. They gave them away free. You picked from a list, no limit, and they just gave them to you. These maps were all really old maps. I mean some were well over 50 years old. The maps their selves were not old, but they were mapped out that long ago. When there I asked if they had any older maps, but no. I was really happy with that.
My map program will connect to my gps and I can download or upload data to my map or gps. I can also print out areas of a map. Plus there are a number of tools included in the program that once learned, are invaluable.
There are a number of map programs. I chose National Geographic because they are well known and established, and I think I picked the best of the bunch, although it was a tough choice.
Right now the entire set for Missouri costs $99 from National Geographic, you can probably beat that price at Amazon or even doing a google search for the program. I assume that the other States are the same price. Either way, my paper maps are all tucked away and safe and I never use them anymore.