In 1813, at the age of nine, Richards moved with his family to Richmond in western Massachusetts. He continued his schooling and obtained a teacher's certificate at age sixteen. He taught school in Chatham, New York, and in Lanesborn, Massachusetts. He completed additional studies and experimentation in the fields of mechanics and science, which led to his lecturing in the surrounding areas on these subjects. During this time he also developed his musical talents and performed as a clarinetist with the Massachusetts Militia Band.
When his sister Susan died of a mysterious illness, Richards took an interest in the study of medicine, including herbal remedies. At the age of thirty, he spent two months at the Thomson Infirmary in Boston, after which he was commissioned as an agent for Thomson's Patent Rights herbal medicine. He then settled in Holliston, Massachusetts, where he practiced medicine and became known as Dr. Willard Richards.
Richards was also interested in religion. He became converted as a teenager to his parents' Congregational faith, but when he was seventeen his application for membership was rejected. He consequently developed a skepticism toward organized religion. However, in the summer of 1836, Brigham Young and his older brother Joseph, Willard's cousins, visited the Holliston area as missionaries for the Church of Jesus Christ of Latter-day Saints. They introduced Willard to the Book of Mormon and taught him concerning Joseph Smith and the claims of restoration of the true church. Shortly after their visit, Willard sold all his medicines, closed down his practice, and moved to Kirtland, Ohio. Other members of his family followed him, and on New Year's Eve he was baptized in icy water by Brigham Young.
Being a single man, Richards immediately was called into missionary service. He first went to New York and New England with Brigham Young to visit family members. Then in June 1837 he traveled to England with other missionaries to open a mission in Great Britain. While in England, he served as assistant to the editor of the Latter-day Saints' Millennial Star.
In England, two great events in Richards's life took place. The first was his marriage in 1838 to Jennetta Richards. Two sons were born to them in England; the first died several months after birth, however. The second great event was Willard's call to be a member of the Quorum of Twelve Apostles. He was ordained an apostle in 1840 in England by Brigham Young.
Willard, Jennetta, and their son left England in April 1841 and settled in Nauvoo, Illinois, where Willard served as a land agent, a member of the city council, and editor of the Times and Seasons. He also was appointed the general clerk and recorder of various community organizations, including the city council and the Nauvoo Temple. In December 1842 he was called to be the LDS Church Historian and Recorder, a position he held until his death.
In 1841 Joseph Smith asked Willard to be his private secretary. In this capacity, he recorded much of the Mormon prophet's activities. He was with Joseph Smith, Hyrum Smith, and John Taylor in Carthage jail when Hyrum and Joseph were murdered. He supervised the removal of their bodies and gave counsel to the church during that troubled time.
As LDS Church historian, he was responsible for keeping the diary of Joseph Smith and was greatly involved in the writing of the history of Joseph Smith. He wrote a total of 1,884 pages of that history, which later was edited by B.H. Roberts and published as the History of The Church of Jesus Christ of Latter-day Saints.
Richards and his family left Nauvoo in February 1846 and spent the year at Winter Quarters. He traveled with the first company of saints to the Salt Lake Valley, returning to Winter Quarters that fall. When the First Presidency of the church was reorganized in the fall of 1847, he was made second counselor to Brigham Young. As the Saints settled in the Salt Lake Valley and organized the provisional government of the State of Deseret, Richards was appointed the territorial secretary. In 1850 he was appointed the founding editor of the Deseret News. He died 11 March 1854 at the age of forty-nine.