This review recounts the advance of amateur radio from 1912 -- the last year that U.S. amateurs operated without licences -- to 1921. In 1912, none of the Chicago Wireless Association members had a transmitting range greater than 90 miles (145 kilometers). However, nine years later, Ralph H. G. Mathews, who in 1912 had only transmitted a distance of 4 miles (6.4 kilometers), was now being heard nearly 3,000 miles (4,800 kilometers) away, over his Special Amateur station, 9ZN.
QST, March, 1921, page 30:
AN interesting piece of radio literature has found its way into our cubbyhole--the 1912 official call list of the Chicago Wireless Association. It was printed only nine years ago, but that takes it back to Ye Goode Olde Days in Amateur Radio, because, as we have often said, things have a way of moving fast in this game of ours.
    When this book was printed the Radio Act of 1912 had not been passed and two-letter calls were used, with the Morse code the standard instead of Continental. The rudiments of the now famous Chicago Plan are evident in the association's old "Rules," and some of their agreements are golden today. For instance: "Contention for the use of the air is a waste of time and is prohibited;" "Avoid all unnecessary repetitions, such as 'OM,' 'GE,' 'HI,' etc.;" and this one: "Members of the Association are requested to use tolerance and forbearance in their dealings with others." Others of the rules, however, are an interesting commentary on the development of Citizen Radio.
    Rule No. 22 says that members must not call government or commercial stations Most of the present day amateurs have no idea that such a thing was ever done but it was. And get this you men: "Rule No. 10--Members will not use transmitting apparatus after 11:00 p. m." Shades of the original Boiled Owl! and today DX does not start in Chicago until 11!
    Many familiar names are among the old list, among which are W. J. McGuffage, old "MS" and the association's Chief Operator with the maximum DX record of those days of 90 miles; "HD," Mr. A. A. Howard; "RO," Roy Haynes; "GX," F. H. Schnell, our Traffic Manager of today; "PF," P.  S. Pfeifer; and believe it or not, the entry that made us think of the wonderful development separating that day and this: "RM--R. Mathews, 5030 Kenmore Avenue; miles worked 4."
    Yes, it must be true--it's our own Matty of 9ZN. Can you imagine a 9ZN with a proud record of 4 miles? Don't you believe us when we say that we have progressed?
    Think of 9ZN of today, with a record of close to 3,000 miles, and copied innumerable times in every state in the Union: go back just weeks and recall the Transcons, with that same "R. Mathews" at his key in Chicago spanning the magnificent distance to Roswell, New Mexico, as easily as tho it were a small fraction of his original four miles, and making possible our Transcontinental record of 6½ minutes.