For those of you not familiar with Flagstaff, we sit in the mountains of northern Arizona at an elevation of 7000 ft. (about 2300 m.) above sea level. This can make for some interesting baking (and cooking to a lesser extent) experiences.
The atmosphere is thinner here so the pressure is lower and there is less oxygen. Water boils at a lower temperature. Roughly, the temperature at which water will boil drops just under 1º F per 550 ft. At sea level it boils at 212º F, so at 7000 ft. it boils at approximately 200º F. This means that food takes longer to cook. For cooking all that is usually required is a longer cooking time.
Baking is something entirely different. Due to the decreased air pressure breads rise more rapidly, then fall and bake into a dense loaf of disappointment. When baking quick breads or muffins, simply decrease the leavening agent by 25%. When baking yeast breads there may be more fine tuning involved. I have had to play with decreasing the yeast, sugar or both. Other variables come into play as well, such as what type of flour you are using. Here is a comprehensive guide to high altitude baking/cooking published by Pillsbury. It is the best guide I’ve ever run across. http://www.pillsbury.com/Recipes/High-Altitude-Guide