Short answers, pulled from the story.
The National Television System Committee issued its first technical standard for black-and-white television in March 1941. This standard was based on a 1936 recommendation by the Radio Manufacturers Association and selected 525 scan lines as a compromise between competing proposals.
The Federal Communications Commission unanimously approved the NTSC color-television standard in December 1953. This standard, later defined as RS-170a, retained backward compatibility with existing black-and-white sets and introduced a color subcarrier of 3.579545 MHz.
NTSC broadcasters in the United States were required by the FCC to shut down their analog transmitters by the 17th of February 2009, though the shutdown was later moved to June 12 of that year. Most over-the-air NTSC transmissions in the United States ended on the 12th of June 2009.
The NTSC standard was adopted by other countries including Japan and several in the Americas. North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries such as Japan are adopting or have adopted standards other than ATSC.
The NTSC system was plagued by reception problems that could degrade the color accuracy of the picture, including ghosting that changed the phase of the colorburst. Vacuum-tube electronics used in televisions through the 1960s led to technical problems that required the inclusion of a tint control on almost every set.
A transmitted NTSC television channel has a total bandwidth of 6 MHz. The video signal is amplitude-modulated and transmitted between 500 kHz and 5.45 MHz above the lower end of the channel, with the video carrier located 1.25 MHz above the lower end of the channel.