John DeCow, also known as John DeCew or John DeCou was a United Empire Loyalist who played a part in the early history of the Niagara Peninsula and the War of 1812. John was born in New Jersey on 03 February 1766, the son of Jacob DeCow of Lincolnshire, England. The family were Huguenots who had come to the New World in the early 18th century, eventually establishing themselves in a Huguenot colony in the area of Philadelphia, Pennsylvania. DeCow died on 25 March 1855 in Decewsville, Ontario at the age of 89.^[1][2]

After the American Revolution, during which he remained a loyalist, John DeCow sought refuge in the Niagara Peninsula in the late 1780s. He took work as a surveyor for the Crown (George III) in 1788. As a consequence of his work, he was able to acquire a mill site and a tract of land in what was to become Thorold Township. The mill site was located on a tributary to the Twelve Mile Creek, at what is now called the DeCew Falls. John married Catherine Docksteder on 9 August 1798.

Although the mill, completed in 1792, was one of the first sawmills in Upper Canada, it did not prosper over the long term. Nonetheless, the area around DeCew Falls attracted a fair amount of settlement and business development that lasted well into the next century. DeCow prolonged the life of his mill by adding grist mill and linseed milling capabilities with the financial support of Robert Hamilton of Queenston. In addition, DeCow constructed a stone house, which has since come to be known as DeCew House, on the Beaverdams Creek near a place on the Niagara Escarpment that commanded an impressive view of the lands below.

At the start of hostilities in the War of 1812, DeCow had already been a commissioned officer in the King's militia for 15 years. He volunteered his house as a headquarters and supply depot for the British army operating in Niagara. He was placed in command of the 2nd Lincoln Militia. After engaging the Americans at the Battle of Fort George, DeCow was captured by the Americans during the retreat of his regiment from Niagara-on-the-Lake on 29 May 1813. He was imprisoned at the Philadelphia prison then known as the Invincible. He escaped custody on 20 April 1814 and began to make his way back to Niagara, despite a broken foot.

During DeCow's absence, Lieutenant James FitzGibbon had been maintaining his headquarters at DeCew House. It was to that house that Laura Secord is said to have made her famous 32 km trek to warn the British of an impending attack by the Americans ensconced, at that time, at Queenston. At was is now known as the Battle of Beaver Dams, the British defence, spearheaded by several hundred Mohawks and Odawa warriors, managed to capture the American 14th Infantry and three detachments from other units along with a mounted unit. The American offensive was under the command of Colonel Charles Boerstler. Boerstler and 484 other men were taken prisoner in what was to prove a pivotal point in the war.

In June 1814, DeCow, after having been significantly aided by pacifist Quakers in the US, rejoined his unit in Niagara. DeCow remained with his regiment well after the cessation of hostilities, retiring from the militia in 1823 at the age of 57.

After the war, DeCow made substantial efforts to revive and to keep vital his milling operations at DeCew Falls. Ultimately, the challenge of inconsistent water flows spelt the end for his mills. In the 1820s, DeCow began to throw his lot in with the entrepreneur and industrialist from Shipman's Corners, William Hamilton Merritt. Merritt recruited DeCow with promises of increased water flow and traffic through the Beaver Dams and DeCew creeks as a consequence of the construction of the Welland Canal. In fact, the original proposal for the canal alignment, in 1818, would have routed traffic through the DeCew Creek, to DeCow's great benefit. As a result of these plans, DeCow and Merritt joined with several others to become charter members of the Welland Canal Company. Once the plans had been finalised, though, the canal ended up taking a route along the Twelve Mile Creek, leaving DeCow without financial gain and actually diverting water from the DeCew Creek into the new alignment. Thereafter, DeCow and Merritt remained life-long enemies in matters of business as well as socially and politically. In 1825, DeCow withdrew his entire investment of stock from the Welland Canal Company. In about 1829, DeCow came up with a new plan to revitalise his holdings at DeCew Falls. He proposed to build a window-glass manufacturing plant but he was further disillusioned when the government of the day refused to pass the articles of incorporation for the new company.

Between 1830 and 1836, DeCow spent much of his time petitioning the Government of Upper Canada and the Welland Canal Company for recompense for his perceived wrongs at the hands of Merritt. In the end, some compensation was finally paid but DeCow, apparently unsatisfied, never forgave Merrrit for what he felt to have been Meritt's treachery. In 1831, John Warren, member of the Parliament of Upper Canada representing Haldimand Riding, died while in office. In the by-election of November 1832, W.H. Merritt secured the governing party's nomination to replace Warren on the government benches; DeCow used his Methodist connections and threw his hat into the ring under the banner of William Lyon Mackenzie's Reform opposition, running against Merritt. As the campaign progressed, DeCow showed surprising strength, forcing a worried Merritt to secure the intervention of the celebrated and well-known Colonel John Clark of Niagara in Merritt's behalf. Despite Clark's endorsement, DeCow was only narrowly defeated by Merritt in the election. DeCow continued his opposition to Merritt and the Canal Company. In the General Election of October 1834, DeCow campaigned actively for David Thorburn of the Reformers in the Third Lincoln Riding. J.J. Lefferty was declared the winner on the government side but, after an appeal (similar to a recount), the victory was awarded to Thorburn as of February 1835. In 1836, amid growing dissatisfaction with the Family Compact, DeCow led the opposition in Thorold Township to what, at that time, was felt to be excesses of government. Despite his activism, there is no evidence that he took any part in the Rebellion of 1837.

About 1834, DeCow was growing increasingly frustrated with his situation in Thorold and he grew eager to try again to seek his fortune elsewhere. He moved to an area that had been part of the Six Nations land grant; within six miles (10 km) of the Grand River in what was known as North Cayuga Township. Again, DeCow erected a sawmill but he also made plans to build a glass factory. In 1835, he established the Cayuga Glass Manufacturing Company. The following year, the distractions of the rebellion and his preoccupation with leading the opposition in Thorold supposedly caused the company's charter to expire. DeCow continued his efforts to establish a glass works until 1845 when, finally, the Legislature once again failed to allow the articles of incorporation. At the same time, DeCow had made a lasting industrial expansion in the area with a thriving sawmill and lime kiln. These had attracted substantial agricultural interests to the area, as well. By this time, the small hamlet of Decewsville had sprung up in the area.

By about 1851, at the age of 85, DeCow had retired. Despite his advanced years, however, he remained a keen political observer. MacKenzie's Reform victory in Haldimand that year prompted DeCow to speak out again against the Family Compact and against big government. Three of DeCow's sons also were politically active, militating in favour of MacKenzie's various reforms and investigations of government excess. In 1853, at the age of 87, DeCow's son, WIlliam, conveyed to MacKenzie the sentiments of his father, asking why he couldn't see MacKenzie more often and congratulating him on his part in the downfall of the Tories.

DeCow died 25 March 1855 at the age of 89. He is buried at Decewsville, Ontario.