What's the standard side arm(pistol) of the US police?

I have researched, and most people said a variety of glock pistols, Beretta M9s, some S&W revolver models, SIG pistols, and I don't know anymore. The standard caliber for the pistols were: 40. S&W, .44 mag, .44 special, 9mm, .357 mag, and I don't know any others.