The telegraph was invented in 1844. The devices developed to hold the electrical transmission wires to the poles were called insulators. The telephone, invented in 1876, also intensified their usefulness, and by the turn of the century, thousands of varieties were being produced in pottery, wood, and glass of various colors. The most common glass insulators today are in light aqua blue color. These usually sell for $1 at flea markets and garage sales around Washington County. A cs726 glass insulator in the color of red recently sold for $26,640 at Ray Klingensmiths Glass Discoveries Auctions in Parkman, Ohio. A cd 726 blue example (cd stands for consolidated design) sold for $8,400 and a bright aqua cd 736 E.R.W. (Erie Railway) sold for $10,080. If you have glass insulators you feel may be valuable, contact Ray Klingensmith at P.O. Box 628, Parkman, Ohio 44080 or give Klingensmith a call at (440) 548-5408 or e-mail Ray at email@example.com. Klingensmith also specializes in the sale of old bottles and other glass, and has set world records in doing so.