Well, that wasn’t always the case.
The Museum of the City of New York has an exhibition on now “The Greatest Grid,” marking the centennial of Manhattan’s famous street plan of 1811. There you can see the original hand-drawn map showing the twelve avenues that were designed to run the length of the island, starting at Houston Street.
East of 1st Avenue, however, were two outcroppings of land. The one between Houston and 14th St. was wide enough to accommodate four additional avenues. Those were given the letter names of A, B, C, and D. The land east of 1st Ave. from 59th St. to 91st St. was only wide enough for two avenues; Avenue A, which became York Avenue in 1928 and Avenue B, which is now East End Avenue.
P.S. 158 Bayard Taylor, between 77th and 78th Streets was built in the mid 1890s, which is why it bears the inscribed address. Read about the renaming of the avenue in honor of Sgt. Alvin York at Inside the Apple (hint, it had to do with money).
Speaking of renamed avenues, I’m happy to report that this lovely vestige of pre-1945 Manhattan still glows green on the wall of a subway exit at Rockefeller Center. I’m always relieved to see it when I’m there, because I can’t imagine it standing a chance of repair if it is ever damaged. The name change of “Sixth Avenue” to “Avenue of the Americas” was also a scheme for increasing real estate values. It just never seemed to take in the same way “York” did. Not as catchy, maybe?
Ephemeral New York reports that we've got the business owners of Sixth Avenue to thank for the name-change:
In the 1940s, they argued that the then-dingy avenue (the El had recently been dismantled above it) needed some sprucing up.
One way to do that would be to get Central and South American countries to build consulates and company HQs on the avenue. Real-estate bigwig Leonard Spear took credit for that idea.
In 1945, city council members were convinced, and Mayor La Guardia signed the name change into law. In the 1950s, signs representing different countries in the Americas went up all along the avenue.