Look for them just above the weather service. The feds use discreet channels without any real organized band plan for their repeaters, so you'll just have to search for them and realize that local police departments aren't gonna be talking about criminals that far up the VHF band. There is some US military traffic just above and below the 2 meter ham band too.
The Post Office and DEA are just below 420 mhz UHF. Much of the federal activity is gonna require a "digital" P-25 scanner even for things like the US Park service now. The FBI, SS, ATF etc are encrypted more often then not, so you're outta luck in that case.
The US Forest Service still uses analog FM radios; because CAL-FIRE and most of the local fire departments are still using older equipment. Once they get new radios by 2013, there won't be much left on millions of analog scanners but the CB and ham radio operators...