Law & Order is an American police procedural and legal drama television series, created by Dick Wolf and part of the Law & Order franchise. It originally aired on NBC and, in syndication, on various cable networks. Law & Order premiered on September 13, 1990, and completed its 20th and final season on May 24, 2010. At the time of its cancellation, Law & Order was the longest-running crime drama on American primetime television. Its record of 20 seasons is a tie with Gunsmoke (1955 -- 75) for the longest-running live-action scripted American prime-time series with ongoing characters. Although it has fewer episodes than Gunsmoke, Law & Order ranks as the longest-running hour-long primetime TV series. Gunsmoke, for its first six seasons, was originally a half-hour program.

Based on this passage, when did the show law and order start? Let's think fast. Stream of consciousness:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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To answer the question, consider the following: Law & Order premiered on September 13, 1990, and completed its 20th and final season on May 24, 2010. So the final answer is September 13 , 1990.