There are other important things to look at besides mountains and places to backpack (although that was #1 with me, too). You probably don't need these at the time you retire (although I needed them for almost a year when I was 60 due to vision issues requiring multiple surgeries), but you will eventually. Unless you want to pack up and move again when you're already getting decrepit, you definitely need to factor them in for your retirement home.
Availability of medical care.
Availability of public transportation, to get to said medical care, grocery shopping, social life, cultural events, and/or church. Eventually we all have to give up driving, some sooner than later. As mentioned, I got an early taste of that with my detached retina requiring multiple surgeries. I had a rapidly advancing cataract in the other eye (which they didn't want to remove until the retina was stabilized), so my car sat in my garage for almost a year.
Closeness to friends and family. This can be important when, for example, you have to have even minor outpatient surgery and need someone to stay with you around the clock for the first day or two. It costs a lot of money to hire someone for this, if you can even find anyone to hire.
Taxes. Some of us would like to keep what we've saved up! California has the highest income and sales tax rates in the country. Oregon (where I live) has income tax but no sales tax. Washington has a high sales tax but no income tax. Washington has (or at least used to have) property tax exemption for seniors.
I originally was going to move to the east (dry) side of the Cascades in Washington, but ended up staying in Oregon just east of Portland. I'm really close to the Columbia River Gorge for year-around hiking and, of course to the Cascades. This area has reasonably good public transit available and I can reach high quality medical care. There are two supermarkets within 1/2 mile. I can take public transit to downtown Portland for cultural events. One of my children lives 3 1/2 hours away and two more live about 13 hours away.
I would really have loved to go back to Wyoming, where I grew up--preferably Pinedale or Dubois. It's a really wild place (which I love), and the people there are wonderful. However, the winters last 9-10 months of the year and are frightful. After 37 years of living with relatively mild winters, there's no way I could stand that. Medical care is also a problem; for more than routine care you end up in Denver or Salt Lake City, a long drive away. Public transport of any sort is pretty much non-existent--there is not enough population to support it. The only way I could live there would be to have family close enough for everyday support, and that won't happen.
I don't necessarily recommend where I live, but when I factored everything in I decided to stay put where I already was. Your mileage definitely will vary!
The suggestion of trying several areas before settling down is a good one!