Online help for the identification of Goldenrods: 1, 2, 3. and Goldenrod galls: 1, 2, 3.
Sometimes herbaria disagree over which binomial should be the accepted name and which names should be synonyms for the accepted name. Such is the case for the species below. This site will usually adopt the position taken by the Flora of North America.
Here are two websites that examine the rationale for these choices.
1. Integrated Taxonomic Information System
2. The Plant List