Which decade is considered to be the beginning of America's Jazz Age?

This is not accurate. Jazz originated in the African-American communities of New Orleans, Louisiana, in the late 19th and early 20th centuries. It developed out of many forms of music, including blues, spirituals, hymns, marches, vaudeville song, ragtime, and dance music. It was already well established by the 1920s - it didn’t start then.

I love the Jazz era & those musicians especially Louis Armstrong! “ I ❤️his rendition of “What A Wonderful World.”