Original sentence: KDKA has described itself as the "Pioneer Broadcasting Station of the World", and traces its beginning, initially using the temporarily assigned "special amateur" call sign of 8ZZ, to its broadcast of the 1920 Harding-Cox presidential election results on the evening of November 2, 1920
Edited sentence: Although at least one other commercial radio station had been broadcasting earlier (Montreal's XWA), KDKA has described itself as the "Pioneer Broadcasting Station of the World", and traces its beginning, initially using the temporarily assigned "special amateur" call sign of 8ZZ, to its broadcast of the 1920 Harding-Cox presidential election results on the evening of November 2, 1920