The Thea Foss Waterway is the best bet for running in downtown Tacoma. It’s the finger of harbor that lines eastern Tacoma. Just off of Dock Street, runners will find sidewalks and a concrete walkway around the marina. The public esplanade starts at the Dock Street/East 15th St. intersection and continues south to 21st Street Park. It’s ~1.7 miles one way.
ADD-ON: Nearby Wright Park is a lovely arboretum and botanical garden along South St. There’s a nice network of paths. A perimeter loop is ~1 mile. To access from the Thea Foss Waterway, use either S 11th St. or S 4th St. to cross I-705.