The route's most important community is the town of Placentia, which is home to the province's only lift bridge.

Route 100 also serves as an access to the Marine Atlantic ferry to Nova Scotia, which is located in Argentia.

It turns north and passes through the actual community of Placentia before crossing a lift bridge into Jerseyside.

The highway now has an intersection with a local road leading to the Castle Hill National Historic Site before passing through Freshwater.

The highway leaves the town limits and heads northeast along a river valley to have an intersection with Route 101 before passing by Fitzgerald's Pond Park.