Alger is a census-designated place (CDP) in Skagit County, Washington, United States. The population was 403 at the 2010 census. It is included in the Mount Vernon–Anacortes, Washington Metropolitan Statistical Area.
The crossing of the St. Croix River was difficult for the railway, since the original bridge across the river was very low and trains had to contend with steep grades on both sides of the river. This made it necessary to use helper engines and to make trains shorter.