Following up on the 1925 American Labor Press Directory data set, I’ve worked up a set from the 1940 volume of the same title. Unlike it’s predecessor, the 1940 volume reflects the mainstream status of the labor movement. It was compiled through a WPA project directed by labor economist John R. Commons at the University of Wisconsin.
Of the 680 newspapers listed, only a couple radical papers remain, and there are no (zero) non-English papers. The 1925 directory had about 60 non-English newspapers. Some drop off might be attributed to the passing of the immigrant generation, but more likely that Commons, et al. didn’t think it was important. Still, the 1940 volume reflects the geographic spread of unionism after 1935 with many more papers on the west coast. You can search the data set here. There is also a 1946 “Labor Who’s Who” that includes a much smaller Press Directory. Still waiting on a better quality scan to get the whole directory.