Samuel Cushman Caldwell was born on April 10, 1836 in the west end of Old West at Dickinson College in Carlisle, Pennsylvania. His father, science professor Merritt Caldwell, and his mother had their home on the first and second floors of the college building. Professor Caldwell was forced to resign from his position at Dickinson in March 1848 due to poor health. He died soon after in Portland, Maine. There, the younger Caldwell lived with family, preparing at the Hebron Academy for college. In 1855, Samuel Caldwell returned as a student to Dickinson College, where he was elected to the Union Philosophical Society and graduated with his class in 1858.
Caldwell taught Greek and Latin in Maryland and at the Rock River Seminary in Mount Morris, Illinois. He then returned to Portland, Maine to study law. Caldwell was admitted to the bar there in 1863, but took up journalism instead. He worked for The Methodist as assistant editor to George R. Crooks, one of his father's former students of the Dickinson class of 1840. Caldwell stayed with that publication for almost four years between 1866 and 1869, then joined the editorial staff of the New York World. After three years, he took a similar position with the New York Tribune in 1872. Caldwell remained there until his retirement, serving as night editor, editor of the weekly, and editor of the semi-weekly. In 1902, he became editor of the New York Tribune Farmer and worked there until the publication was discontinued in 1911. In civic affairs, Caldwell served in 1896 as president of Pelham Village, the town where he lived.
In March 1883, Caldwell married Carrie Forshee of New York City. The couple had no children. In 1899, his alma mater gave him an honorary degree and the Dickinson chapter of Phi Beta Kappa awarded him his key. On March 3, 1923, Samuel Cushman Caldwell died of pneumonia in Pelham Village. He was eighty-six years old.