Short answers, pulled from the story.
Monroe H. Rosenfeld wrote a column in the New York Herald that first used the phrase Tin Pan Alley in 1903. The article described the clashing sounds of many cheap upright pianos playing different tunes at once.
Willis Woodard and T.B. Harms were two enterprising publishers who moved their companies to New York City in the late 19th century. They specialized in popular songs rather than hymns or classical music which had dominated earlier markets.
A group of Tin Pan Alley music houses formed the Music Publishers Association of the United States on the 11th of June 1895. The association unsuccessfully lobbied the federal government in favor of the Treloar Copyright Bill which sought to change copyright terms from 24 to 40 years.
On the 2nd of April 2022, 28th Street between Broadway and 6th Avenue was officially co-named Tin Pan Alley by the City of New York. A plaque now commemorates the location on 28th Street between Broadway and Sixth Avenue.
The New York City Landmarks Preservation Commission designated five buildings 47 through 55 West 28th Street as individual landmarks on the 10th of December 2019. This action followed a concerted effort by the Save Tin Pan Alley initiative of the 29th Street Neighborhood Association.