In 1847, at age 19, he moved to New York City to become an author and, with the assistance of Mordecai Manuel Noah, began publishing in periodicals while also working at a pencil case engraving factory.

Trowbridge wrote numerous works under the pseudonym of Paul Creyton, including The Midshipman's Revenge (1849), Kate the Accomplice, or, The Preacher and the Burglar (1849), The Deserted Family, or, Wanderings of an Outcast (1853), Father Brighthopes, or, An Old Clergyman's Vacation (1853), Burr Cliff: its Sunshine and its Clouds (1853); Martin Merrivale: His X Mark (1854), Iron Thorpe (1855), Neighbor Jackwood (1857).

He is today perhaps best remembered for his study The South: A Tour of Its Battlefields and Ruined Cities[6] (1867, republished two years later with additions by another author as A Picture of the Desolated States and the Work of Reconstruction, 1865-1868).

He observed carefully, and talked with a wide variety of people of both sexes, including freedmen, die-hard Rebels, Unionists, farmers, businessmen, refugees, and Northern entrepreneurs.

His book can profitably be read with those of John Richard Dennett (The South As It Is: 1865-1866) and Whitelaw Reid (After the War: A Tour of the Southern States, 1865-1866).

All three accounts are written from the perspective of a loyal and fair Northerner genuinely concerned about conditions in the South and the evolving policies of the United States towards that section.