This scholarly article, originally prepared for publication in the Ecological Society of America’s quarterly Ecological Monographs (Vol. 42, no. 2) in the Spring of 1972, is offered here as a paperback booklet prepared in 1977 for the author by Hope Farm Press to benefit local historians and naturalists. This fascinating study compares the change in tree species as identified by surveyors in the Catskills during the 18th century with those species identified by the author during field work in the 20th century. Thus, McIntosh’s monograph offers a window into the profound ecological effects of European settlement and the spread of forest industry on the mountains which continue to be celebrated as America’s first great wilderness and artistic muse.