When he was fourteen he joined the Royal Navy, and two years later, after being deemed medically unfit to serve in that branch, the British Army.

He served in the Peninsular War, where he was wounded four times, and by the end of that conflict was a decorated Captain and the Aide-de-camp to General Thomas Picton.

Although identified with the reform movement, Baldwin opposed the rebellion of 1837 and lead 1,200 men, at his own expense, to protect Niagara from rebels.

A distant cousin of Robert Baldwin, he was a politically outspoken advocate of Irish Catholics, opposing the Orange Order and what was perceived as the conservative's affinity for it.

He ran for election as a reform candidate in 1841 in 2nd York riding against the Orangeman George Duggan, but withdrew due to the threat of violence.