In 1758, after three years of war in North America with the French and Indian alliance, the British Empire launched the Forbes Expedition. The campaign began in Carlisle, the county seat for territory that extended to the Ohio River.
The British planned three great campaigns for 1758. One would capture Fort Louisbourgh in Canada. Another would besiege Fort Ticonderoga on the Hudson River. The third would end the attacks on the Virginia and Pennsylvania frontiers by taking Fort Duquesne at the junction of the Allegheny and Monogahela Rivers.
General John Forbes and his second-in-command Colonel Henri Bouquet collected, trained and marched a large force from here west to Fort Duquesne. The force included British regulars and colonial militias, including men and some women from the Cumberland Valley. Local notable campaigners were John Anderson, Hugh Mercer, and James Burd.
Carlisle was the headquarters of the effort when Bouquet and Forbes were here in early summer. It remained the depot and shipping point throughout the campaign. From June to late November, forts were built, skirmishes fought, and the wilderness opened by a well-built road over the mountains. In the face of such determination, and deserted by their Indian allies, the French abandoned Fort Duquesne (later Fort Pitt, then Pittsburgh). With Louisbourg being won by the British in the summer, the tide of the war had turned.
The Forbes Road, as it came to be called, began here on West High Street. It is traceable today as Route 11 from Carlisle to Chambersburg and west along route 30 to Pittsburgh.