The Pearson Report is a good place to start. http://www.webnponline.com/ajnp08.html
AK, AZ, DC, MO, NH, NM, OR, RI, WA, WY all get an 'A' rating for autonomy. MA gets a 'D', BTW. AL, FL, GA, MD, MI, MO, NC, SC, all rated an 'F'.
Other factors some into play, too. Here in CT, as in many other states, we have a collaborative agreement, and if you can find a supportive physician, the prescriptive laws are fairly friendly, and it's possible to have enough autonomy. CT rates a 'B'.