The Welland Canal has been the focus of plots on a number of occasions throughout its existence. However, only two have ever been carried out. The earliest and potentially most devastating attack occurred on September 9, 1841 at Lock No. 37 (Allanburg) of the first Welland Canal [approximately 180m north of today's Allanburg bridge] when an explosive charge destroyed one of the lock gates. However, a catastrophic flood was prevented when a guard gate located upstream of the lock closed into place preventing the upstream waters from careening down the route of the Canal and causing further damage and possible injury or loss of life. It was suspected that Benjamin Lett was responsible for the explosion.
The next act of sabotage wouldn't occur for nearly 60 years. On April 21, 1900 about 6:30 in the evening, a dynamite charge was set off against the hinges of Lock No. 24 of the Third Welland Canal (just to the east of Lock No. 7 of today's Canal, doing minor damage. This time, the saboteurs were caught in nearby Thorold. John Walsh, John Nolan and the ringleader "Dynamite" Luke Dillon (a member of Clan-na-Gael) were tried at the Welland Courthouse and found guilty, receiving life sentences at Kingston Penitentiary. Nolan lost his sanity while incarcerated, John Walsh was eventually released while Luke Dillon remained in custody until July 12, 1914.
The First World War brought with it plots against the Canal and the most notable of them came to be known as "The Von Papen Plot".
In April 1916, a United States federal grand jury issued an indictment against Franz von Papen, then a senior German diplomat, on charges of a plot to blow up the Welland Canal. However, Papen was at the time safely on German soil, having been expelled from the US several months previously for alleged earlier acts of espionage and attempted sabotage.
Von Papen remained under indictment on these charges until he became Chancellor of Germany in 1932, at which time the charges were dropped.