See Evgenia Shnayder, "The Rise of the American Railway Union, 1893-94," Spatial History Project website, Stanford University.
Jonathan Garlock, Guide to the Local Assemblies of the Knights of Labor (Westport, Conn.: Greenwood Press, 1982), 61, 550.
See visualization below, "The Rise of the American Railway Union, 1893-94."
Stromquist, Generation of Boomers, 84-86, first analyzed this data using the ARU newspaper, the Railway Times.
Quoted in Stromquist, Generation of Boomers, 86.
U.S. Strike Commission, Chicago Strike, xxxiv.
Checking the addresses against the Sanborn Insurance maps of the period indicates that in California, at least, the address was probably the secretary's home address and not a union hall.