The League of American Bicyclists has released its latest ranking of Bicycle Friendly States. In the eighth annual assessment, Arizona ranked 19th nationally, slipping from 15th last year. Visit bikeleague.org/states to see how all the states ranked and individual states’ report card with more details. Here is a direct link to Arizona’s report card BFS2015_Arizona.pdf
The Bicycle Friendly States ranking is based on a number of key indicators, including infrastructure and funding that provide on-the-ground bicycle facilities; education and encourage programs that promote cycling; and passage and enforcement of bicycle-friendly laws that make it safe and comfortable for people of all ages to ride.

Despite ranking 19th; Arizona has a high percentage of population living in in Bicycle Friendly Communities; see here for more about cities and towns in Arizona that are ranked bicycle friendly.
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So what makes a state bicycle friendly? The League of American Bicyclists summed it up here:  Attributes Of A Bicycle Friendly State