In my opinion, Red's Corner(s) refers to the intersection near the home of John Red as marked on the attached excerpt from an 1878 "Beers" Map of Prince George's County. You can find that same intersection today by plugging the coordinates (38.80380, -76.90704) into the search box for google maps, acme mapper or probably any mapping website. I've attached two screen captures showing that point using today's maps. It's very close to Andrews Air Force Base.
How did I arrive at this conclusion? Ernest's father was Jeremiah Allen per a newspaper article on his son's death. In the 1900 census, Jeremiah and his family were living in the District of Columbia where Ernest was killed. If you go back to the 1880 census, however, you can find Jeremiah and his wife, Martha, still living Maryland -- in the Oxen Hill area of PG County. I assumed that Jeremiah or his wife had family near Oxen Hill and that's where they took their son to be buried. I looked for an historical map of the Oxen hill area. Frederick W. Beers made a boatload of them back in the 1800s for various places in the U.S.. They're invaluable since they are annotated with the names of homeowners. I noticed the home of John Red on the map near a place called Allentown. I'd bet the farm, so to speak, that Red's Corners refers to the area near John Red's home. I compared the old map with a current map (and some others in between) to figure out the coordinates for Red's Corner(s).
It's hard to miss Bells Cemetery near Reds Corners on modern maps. Unfortunately, Ernest doesn't appear to be buried there per find-a-grave or genweb. Maybe he was buried on the farm of some Allen relative. There's also a church shown on the old map. Maybe they have a graveyard. You'll have to do some more research to find the exact location of his grave. I'd look into where his parents were buried when they died. They might have been buried with Ernest.