This chapter examines the prehistory of the search for extraterrestrial intelligence (SETI) prior to 1961. It reviews the first attempts to contact other planets at the scale of the solar system – that is, interplanetary communication (premodern SETI era). We emphasize the latter half of the nineteenth century because many efforts were made at that time to contact our neighboring planets through interplanetary telegraphy. Such a technique became conceivable in the 1860s thanks to many advances in the field of terrestrial communication (electrical telegraphy, telephone). Generally, the pioneers in interplanetary telegraphy proposed to send flashes using powerful lamps and reflectors to reach our neighboring planets, Mars and Venus. Considering their methodology, the early proposals using light flashes could be compared to modern Active SETI, or METI (messaging to extraterrestrial intelligence). The intellectual approach is similar to that of CETI (communication with extraterrestrial intelligence), since the first attempts were expected to be a two-way exchange of information. Even though they remained only theoretical, these attempts demonstrated that basic thought about a universal language had begun as early as the 1860s. At the turn of the twentieth century, new possibilities emerged with the birth of wireless telegraphy and the development of radio techniques used for telecommunications on Earth. Listening to Mars by means of radio waves was sporadically attempted in the 1920s. By the mid-twentieth century, developments in radio astronomy had a decisive influence on the birth of SETI because they allowed astronomers to contemplate the possibility of contact with extraterrestrials at a much larger scale, that of interstellar distances.