For instance: all the states are listed
AZ,CA,CO,CT,DE,FL,GA,HI,IA,ID,IL,IN,KS,KY,LA,MA,MD ,ME,MI,MN,MO,MS,MT,NC,ND,NE,NH,NJ,NM,NV,NY,OH,OK,O R,PA,RI,SC,SD,TN,TX,UT,VA,VT,WA,WI,WV,WY

I want them to be able to choose more than one selection. What is the best
way to do so?