Collins was appointed midshipman from Iowa on January 2, 1834. Promoted lieutenant, November 6, 1846, he was on the sloop Decatur in the Mexican War, taking part in the attacks on Tuxpan and Tabasco. In the Civil War he commanded the gunboat Anacostia in the Potomac, May 28-August 30, 1861, and then the gunboat Unadilla in the south Atlantic blockading squadron, participating in the capture of Port Royal and subsequent operations on the southeastern coast until the summer of 1862. He was promoted commander July 16, 1862, and afterward cruised in the Bahamas in the Octorara. In this service he was notably energetic, making twelve captures from November 1862 to June 1863. One of these, the British schooner Mont Blanc, taken near the tiny British possession Sand Key, brought protests from England and a reprimand, in Secretary Welles’s opinion unjustified, for Collins.
Sent to Brazilian waters in the steam-sloop Wachusett in January 1864, Collins there performed the exploit for which he is chiefly remembered, the capture of the Confederate raider Florida. The Florida entered Bahia, where the Wachusett was lying in October, 1864. While her captain and many of her crew were ashore, Collins at dawn of the 7th attempted to ram her, and after striking only a glancing blow, fired several volleys of small arms and forced her surrender. Then, despite remonstrances from a Brasilian corvette anchored near-by, he towed her out of the harbor and brought her to Hampton Roads.
On Brazil’s protests Collins was ordered to take the Florida back to Bahia, but she was leaking, and after collision with an army transport she sank on November 28, the sinking being declared accidental by a court of inquiry. Collins’s action was what his government wanted, and he found some excuse in privileges permitted the Alabama in Brazilian waters. Apologies, however, were necessary, and Collins on April 7, 1865, was sentenced to dismissal. This sentence was not approved by the secretary, and in July 1866, he was made captain.
In June 1867, while cruising in Eastern waters, his vessel, the Sacramento, was wrecked without loss of life on a shoal in the Bay of Bengal. Collins was suspended, but was reinstated on March 13, 1869, Secretary Welles commenting that he was “an honest, straightforward, patriotic man, ” though without, in his opinion, “particular love or aptitude for the service”. Collins was commissioned commodore January 16, 1871, and was lighthouse inspector until August 1874, when he became rear admiral and took command of the South Pacific Squadron.
He died of malignant pustula at Callao, Peru and was buried in Callao, but in 1876 his body was brought home.