This is what wikipedia says:
According to an interview with executive producer David Hoberman,[2] ABC first conceived the series as a police show with an Inspector Clouseau-like character suffering from obsessive-compulsive disorder. According to Hoberman,[2] ABC wanted Michael Richards for the show, but Richards turned it down (Hoberman doesn't mention whether these events took place before or after the failure of The Michael Richards Show, which also featured Richards as a detective). Hoberman brought in Andy Breckman as creator, and Breckman, inspired by Sherlock Holmes, introduced a Doctor Watson-like character as Monk's nurse and an Inspector Lestrade-like character which eventually became Captain Stottlemeyer.
Although ABC originated the show, the network eventually handed it off to the USA Network. USA is now owned by NBC (NBC Universal).[3] Monk is the first ABC Studios-produced show (formerly Touchstone Television) aired on USA Network instead of ABC. Psych was the second ABC Studios show to air on USA, four years after Monk's debut. On January 12, 2006, USA Network announced that Monk had been picked up through at least season six as one of the "highest-rated series in cable history."[4] Season 5 premiered Friday, July 7, 2006, at 9 p.m. Eastern time. This marked the first official time change for the program, which aired at 10 p.m. during its first four seasons. The change is due to its popularity and to work as a lead-in to the new USA Network series Psych, another offbeat detective program. Monk has followed a consistent format of airing half of its 16 episodes in the summer and the second half in the winter.