Do you have to have the license plate for access to state parks?
I have been told that the license plate is enough, but Colorado Parks & Wildlife also has issued me a placard that can be displayed in any vehicle in which I am an occupant.
For those who may not be familiar with Colorado Parks & Wildlife in general, this is a major benefit when compared to the past 30 years or so during which the State has been closing or heavily regulating access areas. Places I used for parking while fishing the Arkansas River between Canon City and Salida for many years have been converted to "state parks" with required parks pass or daily use fees. Many state parks and forest areas have been converted to "fee only" use. State park passes are about $80 per year with non-transferable stickers for the vehicles, and daily use fees can be $5 per person or so, even for people pulling onto a roadside area to eat lunch from a cooler.
We are fortunate to have over half of the land area of Colorado as public domains, but much of that is administered by the Parks & Wildlife department and user fees have become rather burdensome (with no signs of letting up). State campsites typically charge about $16 per night to pitch a tent, and more for campers, trailers, etc.
Our state has contracted management of many of the active and popular sites to private contractors, and they seem to be rather aggressive in collecting the fees (in return for their contractual payments, of course).
Please don't get me started on Colorado big game licensing, with about half of all licenses reserved for big-dollar out-of-state spenders while Colorado residents must submit applications months in advance to participate in public drawings to see who is allowed to hunt deer, elk, antelope and other tasty critters, maybe seeing a license once every 4 or 5 years or so.
Come and visit Colorado! Our friendly Parks & Wildlife employees are ready and willing to reach in your pockets deeply and repeatedly.