Gracilaria vermiculophylla (Ohmi) Papenfuss, 1967 is a red alga native to the northwest Pacific, but over the last 100 years, this ecosystem engineer has invaded estuaries throughout the Northern Hemisphere. Despite previous studies documenting populations in estuarine habitats in British Columbia, California, and Baja California, our knowledge of its distribution along the North American Pacific is incomplete. In 2017, we surveyed 61 sites from Chusini Cove (Prince of Wales Island, Alaska) to Bayside Park (San Diego Bay, California), spanning more than 23º of latitude. We documented 33 new sites where G. vermiculophylla is currently found, but may have been previously overlooked, or not recognized. Many of these locations were areas of intensive shellfish aquaculture, particularly oysters, and are also important flyover stops for migrating birds, possibly contributing to the spread of this seaweed. Our study fills in the significant gaps in the distribution of G. vermiculophylla in North America, and, as such, will be an important contribution to future studies on the ecological and evolutionary consequences of this widespread marine invasion along this coastline.