Manson came to British Columbia in 1887, where he was employed as a clerk in a general store in Comox.

[1] Manson was elected to the assembly in a 1905 by-election held after William Wallace Burns McInnes was named Commissioner of the Yukon.

[2] He was a member of the province's Executive Council from 1906 to 1907, serving as Provincial Secretary and Minister of Education.

[3] He was defeated by future Premier Harlan Carey Brewster when he ran for reelection to the assembly in 1907.

Running in the new riding of Prince Rupert, he was defeated in the 1916 provincial election by future Premier Thomas Pattullo.