Fergusson was born in 1783 on his family estate at Woodhill, Perth. He was raised to wealth and, although trained as a lawyer and even called to the bar, he never practised, preferring to live the life of a country gentleman. He married Jemima Blair the heiress to the Blair Estate and so increased his wealth.

He was intensely interested in farming and was a founding memeber of ther Highland Agricultural Society. Scotland in the 1820s was characterised by high unemployment caused by the Clearances, as landowners threw their tenant farmers off the land so as to breed sheep. The answer to the Highland Agricultural Society seemed to be emigration but the Society felt that there was little information to help emigrants and even that was suspect. So, in 1831, Fergusson, by then aged 47 and a widower, volunteered to make the journey to Canada at his own expense to record his experiences. That he did, keeping a daily record of everything that occurred. After returning to Scotland, he published a 37-page report for the Society that was a primer for emigrants. The next year he published a book called Practical notes made on a tour in Canada and a portion of the United States.

Fergusson's spirit of adventure had been roused and, after marrying Jessie Tower, he decided to sell up in Scotland and move his family to Canada with his colleague James Webster. He bought property in Flamborough just below the escarpment and built a house, which he named Woodhill after his ancestral home in Scotland. In 1834, he and Webster bought land in Nichol Township and laid the foundations for a settlement that he named Fergus after his ancestor Fergus Mor Mac Erc. He himself never lived in Fergus; he left that to Webster.

Being a farmer by nature, although not hands-on, he used his money to improve the level of farming in Upper Canada. He planted several different types of grain, not just wheat. He practised crop rotation, a luxury most farmers could not afford. He imported pure-bred, short-horned cattle from Britain. He grew grapes and fruit trees. He helped found the Agricultural Society of Upper Canada in 1843. Its first show was in 1846 and it still has a show every year only now it's called the CNE.

He was interested in educating farmers as well as improving farming in general. He encouraged the establishment of a chair of agriculture in the University of Toronto. He also brought Dr. Andrew Smith from Scotland to found a school for vetinarians in Guelph. This is now the University of Guelph.

Although he was interested in politics, he never ran for office. His politics were unexpectedly liberal for an aristocrat like him. He was actively involved in the Reform Party with George Brown. His son, Adam Fergusson Blair, who incidentally changed his name to Blair to inherit his mother's fortune, was a prominent Reform Politician. The village of Blair is named for him.