[Winniesboy]

There are many rivers called Avon all over the UK, as the literal meaning of Avon is simply 'river' (so 'River Avon' is strictly speaking tautologous). The pronunciation depends entirely on the prevailing vowel sounds of the dialect in that part of the country. In the Scottish Highlands, for instance, it sounds more like 'Aahn', with the 'v' silent.

[Graybeard58]

... Thanks for that explanation. It occured to me after I posed the question that that might be the case.
...We certainly have our share of variations in pronunciation and dialect in the U.S.