Cameron, most vegetable seeds are sown, sprout, grow, produce fruit and then go to seed all in one season, because they're annuals. Montana can be difficult because at least parts of it can get snow every month of the year. Some frost protection from simple rebar and clear plastic hoop huts can make a world of difference in a cool climate.
The other thing you would need to find out is how long the average growing season is. You can find that for anyplace in the U.S. by googling a city and 'growing season'. Bozeman, MT is 107 days, tricky at best, if you have to grow all your own food.
Places with short growing seasons need vegetables that grow faster than others of the same type. Zucchini starts producing in 45-50 days, but most of the storable winter squashes take 80-100.
Some kinds need to be started indoors with heat and light, and transplanted when the soil and air are warm enough for them to survive. Without this head start, they will often just reach the point of producing when cold weather hits and you get a crop of almost-ripe, frozen, mushy, rotting fruit. Tomatoes and pepper are a couple of these, as they like a warm start and hate temperatures below 55F, and frost will kill them. Just be aware that when a plant is started indoors or outdoors in a pot or flat, that "65-70 days" on the seed packet is referring to the number of days
from transplant, not from the day you planted the seeds. The Sweet Orange II Tomato (cherry type - very close to the hybird Sungold, but this one is open-pollinated) can start producing in 65-70 days. The large Brandywine heirloom and big beefsteaks can take 75-100 days to get started.
Some vegetables prefer cooler weather and will die or go to seed very fast in hot weather. Peas, lettuce, kale are some of these. Peas and spinach can even take some actual frost and keep growing.
Bush beans (40-60 days) and bush peas (60 days) are usually all ready to pick at once (good for canning or freezing), but pole beans and pole peas start around 70 days and keep producing flowers and beans (or peas) as the vines grow, and keep producing as long as you keep them picked and they don't get hit by frost.
If you have specific climate challenges to deal with, a generic can of mixed seed that was designed more for central California can be an expensive mistake, at best, and a food disaster if you were dependent on it.
Go to Wikipedia's 'list of culinary vegetables' and copy it, and then delete what you don't like. [They also have fruit and herb lists.] Then go through some good seed catalogs and see what varieties are both OP and most suited to your climate. Two catalogs that I like are Bountiful Gardens and Territorial Seed. But try to also find some seed companies from your area or climate, as their offerings may be far more suited to you than one a thousand miles and six climate zones away from you.
Here's the Garden Watchdog site
http://davesgarden.com/products/gwd/ that has search functions by state or country, and they rate the seed companies.
Seeds kept in a warm, humid environment will deteriorate rapidly. Seeds kept in a cool, dry place can be good for years. Seeds that were properly dried can be vacuum-packed and stored in the freezer.
Sue