I've encountered many more immigrants to CO from the Midwest, than from CA. Lots of Texans also. I've only kept track for 50 years, though. CO Springs has the 3rd highest population of veterans of any US city, and is much smaller than the 2 cities w larger Vet populations. Vets who served here, are drawn to retire or live/work after discharge here.
There are all kinds of reasons why people immigrate. We have a huge population. As it grows exponentially, people go where they can have a better life by making more $, Okies to CA during the Dust Bowl. The financial/gov't brain trust of your town recruits and welcomes immigrant people and business. These Chamber of Commerce boosters have one catchphrase: Growth. Turns out that growth is a Ponzi scheme benefitting the developer, the banker, the politician. Read John Nichols' Milagro Beanfield War, or even better, The Magic Journey. Read it w an indigenous person, to whom you and your ilk are immigrants uprooting the wonderful place this used to be. When that land of milk and honey gets too full, the ones who can afford to, leave for a better place. Once they have their nest egg, they can move for quality of life. So if you live somewhere w an attractive quality of life because it is small and outdoorsy, there is an immigration target on you. Jackson & Cody WY, Montrose & Durango CO, Flagstaff AZ, Reno NV, Bend OR, Taos &, Santa Fe NM, Spokane WA. Now ID and MT, it is your turn, and it comes as no surprise. Figure out where this wave is going next, get there early. Enjoy the financial success roundly available as the new place catches on and takes off. Then it is time to start looking for the next last great place. Abbey wrote, Growth for growth's sake is the ideology of the cancer cell. Word to your Chambers of Commerce.
Pumping the brakes on growth in favor of preserving quality of life and the natural world is not on the platform of any Republican committee, state or national. Many Democrats aren't fully invested in having growth pay for its impacts, either. When the West was an infinite garden of Eden, so underutilized by indigenous tribes that they didn't deserve to keep it, unencumbered growth was the tool and mindset Americans embraced. Early on there were signs the great infinite, wasn't. Read Stegner's Beyond the 100th Meridian, about the inconvenient drought realities of the West. Climate Deniers abounded, even then. They broadly promised rain would follow the plow, meaning a magical weather phenomenon would increase rain as soon as the native prairie grass was cut by the plow. Government homesteading programs guaranteed it.