Dow was born in Belleville, Ontario, Canada, on February 26, 1866. His parents were Americans who had moved to Canada when his father could no longer find work in their native New England. Only a few months after Herbert's birth, the Dow family moved back to the United States. They settled first in Derby, Connecticut, then moved on to Cleveland, where Herbert's father got a job at the Chisholm Steel Shovel works. In 1884, Dow entered the Case School of Applied Science (now Case Western Reserve University). He majored in chemistry and became especially interested in the study of brines, a form of salt water. During his senior year at Case, he presented a paper on brines before the American Association for the Advancement of Science.

After graduation in 1888, Dow began to work on methods for extracting bromine from brine by electrolytic methods. He received his first patent on the topic...