Concentration

The original network daytime series, Concentration, aired on NBC for 14 years, 7 months and 3,796 telecasts (August 25, 1958 - March 23, 1973), the longest run of any game show on that network.

This series was hosted by Hugh Downs and later by Bob Clayton. For a brief period in 1969, Ed McMahon hosted the series. The series began in the 11:30 a.m. (Eastern) time slot, then moved to 11 a.m., and finally to 10:30 a.m. Nearly all episodes were produced at NBC's studios at 30 Rockefeller Plaza, New York City.

A once-a-week nighttime version of the show appeared in two separate broadcast runs on NBC. The first edition appeared only for four weeks, from October 30, 1958 to November 20, 1958, with Jack Barry as the host. The second edition was on the air from April 24, 1961 to September 18, 1961, with Hugh Downs as the host.
From: Wikipedia.org