The Great Plain Wasteland, often referred to as "The Great Waste" by locals, refers to the massive stretch of flatland and former prairie that spans most of Kansas. Before the war, it had provided the land from which vast amounts of America's domestic food products were grown and produced, but now the Great Waste is now a mostly empty and barren husk of the fertile land it had once been. Only three bombs were intended for the whole of Kansas, with one aimed at the capitol of Topeka, another directed towards Kansas City, and the last dropped with the intent of irradiating the fertile farmlands of western Kansas. The aftermath left most of Kansas a wasteland completely incapable of supporting most forms of life -- the cruel irony of which caused some inhabitants to believe that the whole land had just become "one great, empty, completely useless waste", from which the nickname supposedly originates.
Vault 42 -
The Great Waste - Though the wasteland is mostly empty on account of its size, a loose collection of farms, trading posts, and small communities have managed to stake their claim on the land. The majority of these settlements are small single-family farms or single-man trading posts that aren't worth committing to memory, but there are some slightly larger towns which have scraped together a semi-permanent existence in the area. Though generally unimportant, it may be advantageous for one to know the locations of some such settlements, just in case.
Top City - In spite of being decimated by a near-direct nuclear strike during the war, the former city of Topeka still remains at least partially standing and by extent partially habitable. However, the city doesn't serve as the home of any friendly settlements, as the only habitable parts of the city are a point of constant contest between numerous raider gangs which blow in from the Great Waste and as a result it changes hands frequently. The only permanent residents of the city are the countless numbers of feral ghouls which also drift in from across the Great Waste in seek of dark places to hide away. The combination of these two threats makes it nearly impossible to settle in Top City, though it's rumored that the city has come to the attention of a rather large group of slavers from somewhere to the south...
Tracktown - The name "Tracktown" is somewhat misleading -- it doesn't actually refer to any one location. Instead, it actually refers to the interconnected system of settlements built out of the remains of railway yards, almost all of which belong to the Union. A typical tracktown is about as large as an average farm or trading post, but they are typically well-defended from Raiders and are generally pretty self-sufficient.
The Station - The largest of the tracktowns and about the closest thing the Union has to a headquarters. It is one of only two friendly settlements that exists in the ruins of Kansas City and as such maintains close ties to its sister city, Gravestone. The Station makes a name for itself as a bustling hub of trade and commerce, though the Union's strict code of conduct and firm hold on the railways of the Great Waste make some more independent settlers hesitant to set up shop inside the Station's walls.
Gravestone - One of Kansas City's only two friendly settlements, Gravestone is famous for its past as the central hub of a cult devoted to the worship of an atomic bomb known as "Plutonius". Since the Brotherhood's confiscation of said device, Gravestone has since become more open to outsiders and flourishes as a sister city to the Station.