After education at the Milton Academy and Boston's Hopkinson School[1] and graduation from Harvard in 1892, he embarked on a business career, eventually becoming a partner in J. M. Forbes and Company.

[3] Previously, during the administration of President Theodore Roosevelt, he had been Commissioner of Commerce and Police in the American colonial Insular Government of the Philippines from 1904 through 1908; and he was Vice Governor from 1908 through 1909.

[2][4] Forbes was an enthusiastic supporter of the summer capital at Baguio designed by Daniel Burnham, and had a country club and golf course added to the plans.

The summer capital drew resentment from local Filipinos, as it put the government at a distance from the people and was paid for with money earmarked for postwar recovery.

In 1908 diary entry, Forbes described how he and the other lawmakers completed their business at Baguio in "about an hour or less" and devoted the remainder of the day to leisure.

[7] Forbes had envisioned the club as a venue for polo and leisure for "gentlemen of a certain class" assigned to work in the Philippines like himself.

[6] In 1921, President Warren G. Harding sent Forbes and Leonard Wood as heads of the Wood-Forbes Commission to investigate conditions in the Philippines.

Forbes was appointed by President Herbert Hoover in 1930 to lead a commission charged with investigating the reasons for ongoing minor rebellions in Haiti.

[2] In 1935, Forbes headed an American Economic Mission to Japan and China to promote good business relations.

His seasonal home Birdwood, a mansion built in the 1930s for him in southern Georgia, is listed on the National Register of Historic Places.