Signal tower

Wigwag depended on line of sight for the messages transmitted by flag, which led to the construction of towers such as this one from sometime in the 1860s. The flags were sizable--the square fabric would typically measure 4 feet per side, but sometimes as much as 6 feet. They were waved at the end of a 12-foot hickory staff, which surely made for quite a workout. (Torches were sometimes used instead; they were more diminutive 18-inch copper cylinders.)