the small organization known as the Signal Corps was founded after the U.S army needed better ways to communicate with their large population

Most of these communication methods were used UNTIL the invention of the telegraph

some people used trumpets as communication for short distance, some used employed runners to get messages to others from long distances (These seem like they can become not effective easily)

Albert J. Myer invented a way of communication in armies/battle fields for the deaf. This originally was made as words being spelled on one's cheek, hand, etc. Objects were used as well (Tables and things similar to that). The converted this language to flag and torch symbols. They were known was "Wigwag".

"Wigwag" required only one flag unlike other signaling with flags.