He worked on a farm when young to help pay to attend Kimball Union Academy.
Whidden taught at several schools in New Hampshire, including Lancaster Academy, and also in Virginia, where he spent time with Congressman Jared W. Williams (a later New Hampshire governor), with whom he studied for the bar exam.
Whidden was admitted to the New Hampshire bar in 1847 and eventually founded a law firm in Lancaster.
Whidden was elected to the New Hampshire House of Representatives in 1849, 1850 and 1867, where he advocated for the passage of the Homestead Act.
In 1855 Whidden co-founded the Coos Mutual Fire Insurance Company.