The "O" line is a single-circuit 115 kilovolt power transmission line built in 1929 by the SOUTHERN SIERRAS POWER COMPANY. The line used very unusual Jeffery Dewitt suspension insulators unlike the common type seen hanging in collections around the country. These are full-skirted and almost have a fog bowl appearance (see photos). The patent date is Feb 1920 and the manufacture date is Nov 1929. It originally ran between a then-prominent steam generating power plant at Seal Beach (near Long Beach) California, and a major power switching substation on Mill Street in San Bernardino (Calectric, which was at the center of the 115kv system at that pre-Hoover Dam time before the higher voltages of 220kv and above came into favor). The "OPEN" line was constructed as an emergency power interconnect between Los Angeles Gas & Electric Company and the Southern Sierras Power Company. The power line was only energized during emergency power transfers—thus it's "open" designation. Interestingly, within a few years of it's completion, it was energized after the 1933 Long Beach earthquake destroyed a portion of the LAG&E Seal Beach steam plant—then the main supplier of electric energy for that area. The original reason that this long distance transmission interconnection was built was that SSPC and the LAG&E were both generating power at 60 cycles, while other closer utilities around San Bernardino generated at 50 cycles. Expensive cycle converters were limiting and technology had not yet produced one which could handle intended interconnection capacities desired. The "O" line terminated at Calectric substation where another power line, built later in the 1930's for the construction of Hoover Dam, originated. It contributed to the overall reliability of construction power on that major Colorado River dam.

Towers were a direct burial type and the conductors were a copper alloy. Few of the original towers (shown) remain today (except at the Thorne residence in Oak Creek Canyon, AZ). I obtained this tower from the Chino Hills Park right-of-way when some of the towers, with the original insulators were being removed for safety reasons by Southern California Edison Company line crews. I also obtained the original porcelain signs off the old line and placed four of them at the base of my tower. Please see other photos in this series. It is very difficult to link them all.

Enjoy! Reed Thorne