In 1843, the Banque du Peuple was born through the Quebec Nationalist movement, to cater for French Canadians, and in 1848 Quesnel was made a director. He served as its president from 1859 to 1865, during which time the bank enjoyed steady growth and tranquillity. Long after Quesnel's death, in 1894 mismanagement at a time of Montreal's economic peak wrecked it, and the bank was eventually forced to close its doors the following year. In 1830, within a park of 240 acres, Quesnel built "Manoir Souvenir", one of the early estates of the Golden Square Mile and so named in memory of his wife. In 1813, at Boucherville, Quesnel married Marguerite Denaut (1791-1820), the only daughter and heiress of Captain Joachim Denaut, a wealthy fur trader who lived at Granville, by his wife Marguerite Chabert. She died in 1820, and their two sons and three daughters all predeceased him too. He adopted a nephew, and one son married and left a daughter.