1972 – "The French Chef" and "The Mod Squad" were presented with open captions, meaning the captions were burned into the video and could not be turned off. Since major networks were reluctant to have open captions on their programs, PBS began testing two different methods of closed captioning. The first was created by the National Bureau of Standards (NBS) and was known as the Line 21 method because it placed captions on a previously unused part of the broadcast bandwidth. The other was a system that broadcast the captions off the edge of the screen. The Line 21 method was chosen in 1976 and is still in use today.  

1980 – The first three closed captioned television series were broadcast. These included The Wonderful World of Disney (NBC), The ABC Sunday Night Movie (ABC) and Masterpiece Theatre (PBS).

1982 – On March 29, 1982, the Academy Awards was the first program to be captioned live using realtime captioning techniques. FAQ page for a detailed explanation of this mandate.

1990 – The Television Decoder Circuitry Act was passed, which mandated that all televisions manufactured for sale in the U.S. after July 1, 1993, must contain a built-in caption decoder if the picture tube is 13" or larger.

1996 – Congress passed the Telecommunications Act. Under this Act, the FCC adopted rules requiring closed captioning of most, though not all, television programming. See the

2006 – On January 1, 2006, the rules under the Telecommunications Act of 1996 went into effect, requiring that all television programs must contain captions, with few exceptions.