[2] He was named for the distinguished naval officer Stephen Decatur, a close friend of his father, and was a direct descendant of George Trenchard (1655–1712), from the village of Wolverton in Dorset, who had come to the United States with William Penn in 1682.

[1] Trenchard attended a school at Gambier, Ohio, founded by Bishop Philander Chase, with the intention of preparing for the ministry, but instead decided to follow the example of his father and uncle Joshua R. Sands, and join the Navy.

During the Second Seminole War Trenchard cruised in the West Indies, and on the coast of Florida, and had a tour of duty in the Mediterranean Sea aboard the sloop Levant under the command of Hiram Paulding.

[1] Promoted to passed midshipman on July 16, 1840,[3] he attended the Philadelphia Naval School, then returned to the Mediterranean in 1841 to serve aboard the sloops Preble and Fairfield.

The ship left Norfolk, Virginia, on December 7, 1857, but a series of mechanical breakdowns meant that she did not get to sea until the 11th, proceeding to Madeira with the former President Franklin Pierce, his wife Jane, and their suite as passengers.

[1] The frigate departed Funchal on January 6, 1858, calling at Jamestown, Saint Helena, where Trenchard visited Longwood House, the scene of Napoleon's captivity and death.

Confederate forces had already sunk several vessels to block the channel, and the frigate Cumberland was in great danger, but Keystone State succeeded in towing her to safety.

On January 12, 1863, Rhode Island left Hampton Roads with the monitor Passaic in tow for Port Royal, arriving safely.

Trenchard pursued several suspicious vessels between Hampton Roads and Havana, then in company with Santiago de Cuba patrolled the Bahama Banks.

Trenchard captured the Cronstadt, a blockade-runner from Wilmington bound for Nassau, Bahamas, with a cargo of cotton, tobacco, and turpentine on August 16.

[1] In October 1864 Trenchard was ordered to tow the new monitor Monadnock from Boston Navy Yard to Norfolk, Virginia, accompanied by the Massasoit and the Little Addie.

Another serious loss was averted after the tow-line parted in a gale and the ships ran for shelter in Holmes's Hole, before making Brooklyn Navy Yard.

Rhode Island then remained at New York anchored in the East River opposite Wall Street, having her guns trained so as to protect Government properties from the threat of mob violence.

[4][5] Trenchard commanded the screw sloop Lancaster, flagship of the South Atlantic Squadron, in 1869–71, then, with the rank of commodore, served for three years as an Inspector of the Third Lighthouse District.