Toronto's decades-long efforts to revitalize the Don River and protect the city against flooding reached a new milestone Friday. 

Waterfront Toronto has removed the last pieces of the wall that once separated the mouth of the Don River and Lake Ontario as a next step in a project featuring a new island that could become home to thousands of people. 

The metre-wide concrete wall, called the North Plug, separated the Don River from the river valley, according to Waterfront Toronto. Its removal mean…