Lawyer, politician, and land speculator are words that describe Sir Allan Napier MacNab but somehow fail to convey the complexity of the man who could be brave yet sneaky, charming yet bullying, moderate yet extreme. He continued to baffle people right up to his death.

MacNab's father, also Allan, had been born at Dundurn, a farm on Loch Earn, in Perthshire, Scotland. The older MacNab joined the Army at an early age and became a lieutenant in Simcoe's Queen's Rangers during the Revolutionary War. After the war, he went on half pay and moved to Quebec. In 1792, he married Anne Napier, and hearing that his old commander had been appointed to Upper Canada, he decided to move there to improve his fortunes. They settled in Newark (Niagara-on-the-Lake). However, by the time the MacNabs got to Newark, all of the best jobs had been taken. The older MacNab had to take such jobs as he could find. After the capital of Upper Canada moved to York (Toronto), the MacNabs moved with it. That was where Allan Napier was born in 1798, the first child to survive infancy. The family lived reasonably prosperously and young Allan was educated at the Home District Grammar School under the Rev. Strachan and alongside many of the other future leaders of the Family Compact.

When the Americans attacked York during the War of 1812, McNab fought with the defenders and joined them in the retreat to Kingston. Young MacNab managed to get appointed midshipman aboard Sir James Yeo's flagship, the Wolfe. The Navy did not suit him so Yeo recommended his transfer to the Army. He eventually ended up in the 100th Regiment. He was in the storming of Fort Niagara in December 1813, followed by the burning of Black Rock and Buffalo. For this work, he was commissioned ensign in the 49th Regiment, in which rank he remained until going on half pay in 1814.

After the war, MacNab came under the influence of D'Arcy Boulton, the Attorney General of Upper Canada and became a lawyer. He also married Elizabeth Brooke, a sister of one of his schoolfriends, in 1821. They had three children before Elizabeth suddenly died in 1826. He moved to Hamilton and set up his own law office, which prospered, soon leading him into land speculation.

In 1830, he was elected to the Legislative Assembly and immediately, with the style of oratory that made him a success as a lawyer, began to exert an influence on the Assembly. Two years later, to highlight his success, he bought the estate of Col. Richard Beasley on Burlington Heights and built a magnificent house, now known as Dundurn Castle. In the meantime, he had married again, to Mary Stuart.

When William Lyon Mackenzie was elected to the Assembly, MacNab saw a natural enemy. By hook or by crook, he schemed to get Mackenzie expelled from the Assembly. Three times Mackenzie was expelled and each time he was re-elected by the voters. When Mackenzie and his supporters eventually rebelled, MacNab was called upon by the Lieutenant-Governor, Sir Francis Bond Head, to lead government forces against the rebels. At first, MacNab demurred, giving way to Col. James FitzGibbon, but when FitzGibbon resigned, MacNab assumed command over the Upper Canada militia against the rebels. After the defeat of the rebellion, MacNab was knighted for his part in suppressing it.

Soon after the rebellion ended, Upper and Lower Canada were united once more. MacNab became leader of the Conservatives in opposition to the reformist Baldwin-Lafontaine government. When the government was defeated in 1844, MacNab became Speaker until 1848, when the Conservatives were defeated. Once again MacNab became leader of the Conservatives. In 1854, the Governor-General, the Earl of Elgin, asked MacNab to form a cabinet. He managed to form a coalition cabinet, becoming premier of the Canadas until he became too ill to carry on in 1856. When he left office, he was created a baronet.

He died in 1862 but did not go without a parting shot at Upper Canada society. His sister-in-law, Mrs. Sophia MacNab, was with him at the end and she revealed that he had had a death-bed conversion to Roman Catholicism. So he was buried according to Roman Catholic rites.