Industrial melanism in peppered moths has been studied most intensively in 
Britain. The first melanic phenotype (effectively solid black) was recorded near 
Manchester in 1848. By 1895 about 98% of the specimens near Manchester were 
melanic, and this once rare phenotype had spread across regions of the country 
blackened by industrial soot. In rural, unpolluted regions, well away from 
industrial centers, the pale phenotype (peppered with white and black scales) 
remained the predominant form. During the latter half of the 20th century, 
following legislation designed to improve air quality, melanics began to decline 
in frequency and are now rare where once they had been common. Similar 
evolutionary changes have occurred elsewhere, but records from outside Britain 
are fragmentary. We have extended previous surveys of American peppered moth 
populations and present a composite picture of the recent decline in melanism in 
northern industrial states-Michigan and Pennsylvania-where melanic phenotypes 
decreased from more than 90% in 1959 to 6% by 2001. We contrast these changes to 
the near absence of melanism in a southern state-Virginia-during that same 
period. As in Britain, the decline in melanism in American peppered moths 
followed clean air legislation.