I did some research on the transmission line that carries the electrical energy from the Hoover Dam to Los Angeles. Keep in mind that this dam was completed in 1936. 

The General Cable Corporation provided some statistical information regarding the line. The total numher of single circuit towers is 2,422 -- producing an average span of 984 feet, with a maximum span of 1,811 feet and a minimum span of 431 feet. The total number of double circuit towers is 257 in a distance of 40.8 miles.

Single Circuit Tower

Double Circuit Tower

I have m my possession an 8" length of the hollow cable which is 1.4" in diameter. It is as rigid as an 8" length of 1 inch pipe. However, the enclosed literature shows, and tells, that the cable was put on reels for shipping and handling.

The designation "HH" was derived from the name of the German company (Hedenheimer) that invented it. This "HH" cable was manufactured during the great Depression, when unfabricated copper metal was selling for 10 cents per pound. To date (April, 1983) most of this conductor has been removed from service. It is interesting to note that the scrap copper, which was worth almost $1.00 per pound in the 1970's, paid for much of the replacement cable called "ASCR" -- aluminum cable steel reinforced.