He is best known for his designs for company town of Pullman, Illinois, the Hotel Ponce de Leon in Florida and Naumkeag in Stockbridge, Massachusetts.

He also maintained a long working relationship with many noted architects and firms of the time including those of McKim, Mead & White, Carrère and Hastings and Horace Trumbauer.

[1] His uncle, Col. Nathan Barrett built one of the earliest industrial parks in the country at "Factoryville" on Staten Island.

[3] Barrett began his training as a landscape architect in 1866 by running his brother's nursery and educating himself in formal designs by available literary sources and with instruction from the family's Irish gardener.

[5][6] His work at Pullman led to other municipal commissions throughout the 1880s and 90s including those at Fort Worth, Texas, Chevy Chase, Maryland, and Birmingham, Alabama.

In 1885 Barrett was hired by Carrère and Hastings to lay out the grounds and surrounding area of the Hotel Ponce de Leon in St. Augustine, Florida.

The success of the commission enabled Barrett to become the foremost proponent of formal garden design in the country.

[4] Following his work in Florida, Barrett began a long relationship overseeing the landscape designs of numerous country houses for noted architects.

[7] Barrett would go one to design many other major American country estates including "Lynnewood Hall" in Elkins Park PA,(design by Horace Trumbauer), "Woodlea" in Scarborogh NY (also by Mckim Mead & White) and "Hammersmith Farm" the Newport home of Hugh Auchincloss.

[1] In addition to his many towns and country estates he also designed numerous parks and public grounds most prominently working under Frederick Law Olmsted for the 1893 World's Columbian Exposition at Chicago, Illinois .