William Wilberforce Chapin was born in Somers, Connecticut on December 2, 1836. His father Oliver, an instructor at Williams College, died in 1852 when William was sixteen years old. Chapin joined the Congregational Church two years later. He graduated from Williams College in 1860, showing a particular aptitude for the natural sciences. That same year he was sent on an expedition to Labrador and Greenland by the Natural History Society of Williams College in order to collect animal, plant, shell, and other specimens. Upon his return, Chapin attended Andover Seminary. During his time at Andover he met Katherine Isabel "Katie Belle" Hayes, the daughter of a Scottish physician who was on a visit to meet Chapin's sister Charlotte, head of Mt. Holyoke Seminary. Isabel had planned to teach botany at Mt. Holyoke, but instead was forced to return home to New Hampshire to care for her ailing mother. William graduated from Andover in 1863 and was ordained on September 24th of that same year. William and Isabel were married two days later on September 26, 1863. In January of 1864, the couple traveled to India with the intention of completing a ten-year missionary assignment together as part of the American Board of Commissioners for Foreign Missions (ABCFM). They were stationed in Pimplus (Pimpulwandi), a rural area about fifty miles from Ahmednagar, and set up their home in a mud hut. Three months after their arrival, William became ill. Eventually he contracted diphtheria. By the time he was able to seek medical care it was too late, and he died on March 22, 1865 at the age of 28, leaving his wife Isabel a widow at the age of 19.