"Past-year cocaine use in 2015 among 12th graders has been essentially the same across regions and varied between 1.8% and 2.3%, with the exception that the West stood out and climbed to 4.4% in 2015 (Figure 5-10b; also Tables 36-38 and Figure 81 in Occasional Paper 86). In past years regional variation in cocaine use was the largest observed for any of the drugs. Large regional differences in cocaine use emerged when the nation’s epidemic grew in the late 1970s and early 1980s. By 1981, annual use had roughly tripled in the West and Northeast and nearly doubled in the Midwest, while it increased only by about one-quarter in the South. This pattern of large regional differences held for about six years, until much sharper declines in the Northeast and West reduced the differences substantially. In recent years use has been in a fairly steady decline in all regions in all grades although in 2015 there was some increase in three of the regions among 10th graders and in the West among 12th graders. For most of the years of the study, the West had the highest level of cocaine use at all three grade levels, but in recent years the differences have not been very large or entirely consistent.
"In all three grades, past-year crack use has almost always been highest in the West, although these differences are considerably smaller today than in the past (Tables 39-41 and Figure 87 in Occasional Paper 86). When crack use was first measured among 12th graders in 1986, there were large regional differences, with the West and Northeast again having far higher prevalence than the Midwest and South. Crack use dropped appreciably in all four regions over the next several years (though prevalence did not peak in the Midwest until 1987 or in the South until 1989, perhaps due to continued diffusion of the drug to areas that previously did not have access). Because the declines were large and very sharp in the West and Northeast, little regional difference remained by 1991, although the West still had the highest level of use. After 1991 or 1992, during the relapse phase of the drug epidemic, there were increases in all regions, but particularly in the West. Again, the West showed the largest increases and the highest levels of use at all three grades, while the other three regions were fairly similar in their annual prevalence of use. In general, all regions showed evidence of a leveling or decline in crack use at all three grade levels in recent years, along with a diminution of regional differences."
Miech, R. A., Johnston, L. D., O’Malley, P. M., Bachman, J. G., & Schulenberg, J. E. (2016). Monitoring the Future national survey results on drug use, 1975–2015: Volume I, Secondary school students. Ann Arbor: Institute for Social Research, The University of Michigan.