John Ennis Searles was born on October 15, 1840, in Bedford, Westchester, New York, son of Rev. John E. Searles.

He was a financier and businessman. He was educated at the New York Conference Seminary of the Methodist Episcopal Church. Searles began his career as a bookkeeper. In 1862, he became involved with the sugar trade and was employed with a West India shipping firm in New Haven, Connecticut. Searles organized the Havermeyer Sugar Refining Company in 1880 by consolidating two Havermeyer companies. In 1887, he became the organizing force in creating the Sugar Refineries Company known as the Sugar Trust. Searles persuaded competing refinery companies in the United States to consolidate operations into a single business controlling the price of sugar and labour in the United States. In 1891, the Sugar Trust was forced to reorganize into a corporation named the American Sugar Refining Company. He was secretary, treasurer, and chief executive officer of the company. He resigned in 1898. He was known as "The Sugar King of America". Searles was involved in many other endeavours, such as the formation of the American Cotton Company in 1896.

In 1862, he married Caroline A. Pettit (1838–1919), and they had five children. He died on October 24, 1908, in London, England, and is buried in Brooklyn, New York.