Sussex was incorporated in but was only officially established as a town on April 29, The settlers were for the most part British Loyalists who had fled the American Revolution in , with many Irish refugees of the potato famine from the midth century settling in the nearby farming communities. In , the Sussex Military Camp was established on the eastern edge of the town. The facility was closed following the Second World War and the town purchased the land to expand the municipal boundaries.
Today the agricultural exhibition and some areas remain as open land on the former site of Camp Sussex. Sussex underwent several changes in the post-war period. In the early s, several local roads were upgraded as part of the Trans-Canada Highway project which saw Route 2 pass immediately north of the town between Fredericton and Moncton.
At the same time, a series of local roads in the Kennebecasis River valley were designated as Route 1 , running from an interchange with the Trans-Canada at Sussex, southwest to Saint John. Sussex is still considered the best strategically located town, being in the center of what has been called New Brunswick's "Golden Triangle". Potash was subsequently discovered in large quantities in the area surrounding Sussex, with the deposit being the second largest in the world after an area in Saskatchewan.
CN Rail built track to serve both mines, which employed hundreds from the surrounding area. Since , natural gas has been produced from the McCully field near Sussex. Sussex also began to see a growing tourism trade, with many flocking to see the collection of wood-constructed covered bridges throughout the central area of Kings County. Eight of these wooden structures are within a ten-minute drive of town hall.
An agricultural fair draws visitors each August marking years in , as well as the establishment of southern New Brunswick's only alpine ski hill in the Caledonia Mountains southeast of the town at Poley Mountain. A popular international hot air balloon festival is held every September, and Canada's largest outdoor flea market each August.
The town entered economic difficulty during the late s after the Cassidy Lake potash mine flooded, resulting in hundreds of lay-offs. At the same time, Route 1 was extended east on the old Trans-Canada alignment to an interchange at River Glade near Petitcodiac and Route 10 was extended on the old Trans-Canada from an interchange with the new Route 2 alignment at Young's Cove Road south to Sussex.
Today, Sussex is primarily a regional service centre for the surrounding agricultural communities of the upper Kennebecasis River valley, as well as a highway service centre on Route 1, the primary highway between Moncton and Saint John, as well as being the most heavily travelled route in the Maritimes to the United States. The town is home to Sussex Golden Ginger Ale , a popular maritime beverage. Sussex claims to be the birthplace of the ice cream cone ,[ citation needed ] Sussex titles itself as the Dairy Capital of New Brunswick.
On October 12, , she attended the opening of a new wing of Sussex Elementary School, unveiling a commemorative plaque at the event. She then visited Princess Louise Park for an agricultural exhibition. While there, it was announced that the community hall would be renamed Jubilee Hall in her honour. Both appearances drew thousands of visitors from Sussex and beyond.