In June, 1777, following the Battle of Short Hills fought near Ash Swamp in Scotch Plains, the American Army retreated before British General Sir Wlliam Howe and headed toward the safety of the Watchung Mountains. The Soldiers were “…in great destitution, some being without tents, blankets, shoes or provisions and under the utmost depression of sprits”. Young Mary Osborn, heart-sick at the plight of the men, immediately “…exerted herself with patriotic zeal to supply their wants, and gave for that purpose everything eatable or wearable that her house afforded”.
At approximately the same time Mary was helping the cause, a Colonial artilleryman fired his cannon in the direction of the oncoming British who were marching down Park Avenue. The shot was misdirected and thudded into the side of the Osborn house. From then on the townspeople referred to the house as the Cannonball House.