For a quick demonstration of geom_sf(), I'm using albersusa to access the laea projected boundaries of the United States as a simple features (sf) data structure, but sf also makes it easy to read various file formats and even convert various spatial objects to sf. There are also a bunch of other R packages that, like albersusa, make it easy to query geo-spatial data as an sf data. The "Reverse dependencies" section of sf's CRAN page is a good place to discover them, but just to name a few: tidycensus, rnaturalearth, and mapsapi. One awesome consequence of using sf is that, since the data structure contains all the geo-spatial information, both plot() and geom_sf() just workTM. The most brilliant thing about sf is that it stores geo-spatial structures in a special list-column of a data frame.