The Merchandise Mart (or the Merch Mart, or the Mart) is a commercial building located in the downtown Loop, of Chicago, Illinois, United States. When it opened in 1930, it was the largest building in the world, with 4,000,000 square feet (372,000 m2) of floor space. The art deco landmark is located at the junction of the Chicago River's branches. The building is a leading retailing and wholesale destination, hosting 20,000 visitors and tenants per day as of the late 2000s.
Television
On January 7, 1949, NBC station WNBQ commercially debuted its television broadcast schedule on channel 5, with a minimum of two hours of programming per day. April 15, 1956, is remembered as "C-Day" at WMAQ-TV, and was described by Broadcasting-Telecasting magazine as "a daring breakthrough the black-and-white curtain." With Mayor Richard J. Daley looking on, NBC President David Sarnoff operated the controls as Channel 5 became the world's first all-color TV station as "Wide, Wide World" was broadcast to 110 NBC-TV affiliated stations across the country. The color conversion project cost more than $1,250,000 with advertising costing $175,000. On "C-Day", three skywriting planes flew over the city, trailing streams of red, green and blue smoke.  WMAQ-TV first installed color equipment in late 1953, with the Rose Bowl parade of 1954 as the first major broadcast. Introduced in March 1955, the first local color program was John Ott's "How Does Your Garden Grow?", featuring the use of time-lapse color film.  Although WMAQ-TV has since moved to NBC Tower about a mile away, and for the most part the 19th floor of the Mart has been turned into office space, one former tenant (Bankers Life and Trust Company) maintained a remnant of the original studios as their video and multimedia department. The former WMAQ space is currently being redeveloped by Flashpoint Academy as a full modern soundstage facility as well as a screening room, backlot, and classroom space over the 19th and 20th floors.  Local regional sports network Comcast SportsNet Chicago has their control room, and broadcasts their live studio programming from the Apparel Center expansion; the studios had been home to previous RSNs FSN Chicago and SportsChannel Chicago.

Q: Are there any other interesting aspects about this article?
A: On January 7, 1949, NBC station WNBQ commercially debuted its television broadcast schedule on channel 5,

Q: What did this have to do with Merchandise Mart?
A: Although WMAQ-TV has since moved to NBC Tower about a mile away, and for the most part the 19th floor of the Mart has been turned into office space,

Q: What notable businesses are using the office space?
A: one former tenant (Bankers Life and Trust Company) maintained a remnant of the original studios as their video and multimedia department.
Why did WMAQ leave the Mart?
WMAQ-TV has since moved to NBC Tower about a mile away,
WMAQ-TV has since moved to NBC Tower about a mile away,