After graduating from Columbia, Cary spent a brief apprenticeship with McKim, Mead and White in New York City.

In the mid-1890s, Cary redesigned some rooms in the Ansley Wilcox House,[5] which later became known as Theodore Roosevelt Inaugural National Historic Site as it was the site where Theodore Roosevelt took the oath of office as President of the United States on September 14, 1901, after the assassination of William McKinley at the Pan-American Exposition of 1901.

Cary designed features on their home at 460 Franklin Street in the Italianate style.

[2] Together they had:[1] Cary was a founder of the Beaux-Arts Institute of Design, served as president of the American Institute of Architects, of which he was a member for 53 years, a director of the Albright Art Gallery, member of the Fine Arts Academy.

The city ultimately returned the donation stating that they could not use taxpayer dollars to fund and pay for the upkeep of the residence.