Henry was a naturalist from the beginning of his childhood. He was born at Cambridge, Massachusetts, on March 3, 1850, and was the youngest of seven children. His parents encouraged his passion with nature so he was allowed to wander and explore. He developed a love of birds, and sometime between the age of 10 to 12 he shot his first specimen. He entered Cambridge High School to prepare for Harvard. There he met a man named William Brewster, who shared the same interests as Henry. Brewster’s knowledge of birds was greater than Henry’s, and their friendship blossomed into a learning experience. Brewster already had begun a collection of birds and eggs, and together they perfected the preparation of study skins. Due to delicate health, Henry was unable to attend Harvard, but instead was invited to go on a voyage to the southern coast of Louisiana where he began his career as a field naturalist.

Henry subsequently went on many trips where he collected and learned more in the field. In July of 1872, he went to Provo, Utah, as a collector for the Wheeler Expedition. His great love of birds fed his hunger to study them in new and uncharted territory. In 1879, the Wheeler’s Survey merged with the U.S. Geological Survey where Henry worked but still devoted his summers to field work out West. In the fall of 1872, Henry met C. Hart Merriam and they became lifelong friends. Henry wrote Merriam many letters about his different field expeditions, usually addressing them “My dear Merriam.” In the summer of 1874, Henry did his most notable work as a collector. He collected many unknown species of birds from Arizona and also made some valuable observations. At a later point, Henry was studying anatomy with the full intention of studying medicine, but he then questioned his decision to continue.

After a not-so-successful trip to Lake Tahoe, he received an offer in 1880 from Major John Wesley Powell to work with the Bureau of American Ethnology. As an ethnologist he began his work by securing information from the Indians of the Pacific Coast States for the Census of 1880. Henry studied the Indians north of Mexico to prepare material classifying the families’ linguistics, with the results of this work published in 1891. In 1907 to 1910, two volumes of Handbook of American Indians North of Mexico were published by the Bureau of American Ethnology. Henry’s previous work and continued study of Indians provided the basis for these volumes. While Henry was in the West during 1883, he was one of the first committee members to prepare a code of nomenclature and a checklist of North American Birds for the American Ornithologists’ Union (AOU). He served two terms as vice-president of the AOU and unfortunately had to decline the offer of president. Henry, among other men, helped organize the Cosmos Club. By 1888, Major Powell was bogged down with the Geological Survey and placed upon Henry the complicated administration of the Bureau of Ethnology, during which time he also aided in the publication of the “Anthropologist.”

In December of 1894, due to failing health, Henry resigned from the Bureau and moved to the Hawaiian Islands to regain his strength. There he became known as a photographer capturing many valuable images such as the native costumes, houses, and other hard to reproduce negatives. By 1905, Henry was back in Washington with the Bureau of Biological Survey and became an administrative assistant, then assistant chief, and finally chief when Dr. Merriam resigned. While Henry was chief of the Biological Survey, a landmark law in American conservation was passed by congress. It was called the “Federal Migration Bird Law” originating as the “Weeks-McLean Act.” He also worked with the Migratory Bird Treaty with Great Britain. His quick wit and droll sense of humor were entertaining and brought joy to colleagues.

Henry became an honorary member of the Washington Biologists’ Field Club in 1905.

He dedicated his life work to the environment and donated his own personal collection to museums. Henry was a true naturalist who continued to work as chief of the Biological Survey until 1916 when he retired due to declining health. He periodically helped out former associates or anyone else he could. He died on August 1, 1930; he was 81. A building at Patuxent Wildlife Research Center is named Henshaw Laboratory in honor of Henry's role as Chief of the Biological Survey.