The names given to roads, rivers, parks, towns, and mountains vary significantly. While you might expect the spelling to be reasonably consistent, it isn't always, even when in close proximity.
Take the Allegheny and Allegany. Pennsylvania has Allegheny County (home to Pittsburgh), most of the course of the Allegheny River, and most of the Allegheny Mountains and Plateau. New York has Allegany County, and a town of Allegany, which is actually in Cattaraugus County. Pennsylvania is home to Allegheny National Forest. Directly across the state line, adjoining the lands of the National Forest, is New York's Allegany State Park. Thankfully, the river and other geographic features don't change name where they cross the border. That would just be confusing.
Southwest of Allentown, Pennsylvania lies the town of Emmaus. Emaus Road runs from the southern outskirts of Allentown to Emmaus. Some maps (Google Maps, Bing Maps) show it as Emmaus Road, some as Emaus Road (Google Earth). Google StreetView images show "Emaus Ave" on the sign at Emaus and 4th Street.
Another example is simpler. Between the towns of Harrison, Ohio and Bright, Indiana lies a road named Jamison Road. Much of it runs along Jameson Creek, a tributary of the Whitewater River.
It certainly makes inconsistencies in spelling more understandable at times. Variant spellings aren't two surprising, really. But variant spellings for two things in close proximity? Really. Much as it grates on my nerves, it happens in the wild.