Henry Larned Johnson Jr. was born on July 11, 1837, in Griswold, Connecticut, to Henry and Almira Johnson. His father was a farmer who owned $5,000 of real estate and $5,400 of personal property by 1860. He grew up and attended school in Griswold before enrolling at Yale University. He graduated in 1861.
He enlisted in the Union army on July 22, 1861, and he mustered in as a commissary sergeant in the 5th Connecticut Infantry. He was promoted to 2nd lieutenant in September 1861 and to 1st lieutenant in July 1862. Then, in 1863, he was promoted to captain and assistant adjutant general. He served on the staffs of General William Birney and General Alfred Terry. He resigned on April 17, 1865.
He settled in Castleton, New York, after the war, and he earned a living as a stockbroker. By 1870, he owned $15,000 of real estate and $40,000 of personal property. He married Caroline F. Leeds around 1873, and they had at least two children: Leeds, born around 1875; and Larned, born around 1879. They moved to Staten Island, New York, in the 1870s. His wife died in the late 1800s, and he died in New York City on September 9, 1907.