The British maintained a large army, a virtual moving city of 6,000 people, that temporarily made Ligonier the second-most populated spot in Pennsylvania, second only to Philadelphia.

Fort Ligonier was a logical place for travelers to break their journey, and with such commercial opportunities in mind, a local resident named John Ramsay (sometimes spelled Ramsey) laid out the street plan, including the space now known as the Diamond.

Traffic shifted from horse-drawn vehicles to the railroad, causing the community's population to drop to 350 according to the 1860 census.

Additionally, the railroad made it easier for Pittsburgh residents to visit Ligonier, causing the town to develop as a summer resort.

[8][10] In 1909–1910, the Ligonier Valley Railroad built an ornate station and headquarters building, which still stands at 339 West Main Street.

In 1952, the Ligonier Valley Railroad ceased operation, due to a combination of overlogging, decline of the coal industry, and the loss of passenger traffic to motor vehicles.

[11] Ligonier and its surrounding countryside are strongly associated with the Mellon banking family,who still owns considerable tracts of land in the area.

According to the United States Census Bureau, the borough has a total area of 0.5 square miles (1.3 km2), all land.