Channel 1 (North American TV)
For standards developed in the United States, television station allocations have commonly consisted of 6 MHz-wide spectrum groupings, known as "channels". The history of Channel 1 usage by over-the-air broadcasting in North American broadcast television frequencies, is divided into three main periods: Prior to 1948 this was the first TV channel number, assigned to the lowest frequencies.
Source: Wikipedia — Channel 1 (North American TV) (CC BY-SA 4.0)