One of the best known of the United Wireless stations, WA, was located atop the Waldorf-Astoria Hotel in New York City.
 
Modern Electrics, September, 1909, pages 253-254:

Wireless  Stations  About  New York

No. 2--Station  at  the  Waldorf-Astoria

    This station without a doubt is the most popular one in New York. It is located on the top of the beautiful hotel, and the lofty aerial stretches its wires clear over one side of the famous roof garden.
    The aerial is quite a big affair, having twelve wires. The stretch between the two steel towers is 236 feet. The towers themselves are 84 feet high, and the aerial is 300 feet above the ground. Each one of the wires is insulated from the spreader by two 10-inch electrose commercial insulators, which are connected "in series", as one single insulator was not deemed sufficient to hold the high potential.
    The operating room is a model in every respect. Operator E. N. Pickerill takes especial pride in having everything spick and span.
    The output of the station is 5 k. w., and is in daily operation with Chicago and steamers far out on the Atlantic. Contrary to other stations, this one has no regulation wireless key, but a common telegraph key, which in turn works the heavy magnet-operated key shown at A. The operator therefore does not actually handle heavy currents.
    The loose coupler shown in the photograph is used almost entirely, and Operator Pickerill states that it is so far the greatest advancement in the new art, as absolute tuning can be had. The electrolytic and carborundum detectors are used in preference to all other types.
Waldorf-Astoria Towers
Waldorf-Astoria station interior