A distribution map for the lower 48 US states (at the county level) for E. angustifolia is attached. Counties that are light blue (aquamarine?) or purple are confirmed occurrences by various botanical sources. Light blue indicates present, purple indicates noxious (but this is more a political, rather than scientific distinction). Counties that are dark blue are merely reflecting in-state occurrence, but not in that county.
The actual image size is larger than the attachment appears, but you should be able to save the map to view the larger size (I believe).
EDIT: A brief note...while the info mapped is rather comprehensive, it is lacking inputs from 2-3 serious botanical journals (but contains the data from 100s of others) which are in the process of being added. With this in mind, there is the potential for it to occur in counties not marked, but generally, it can be fairly safely assumed that such counties would be close to or fall within the general distribution created by the mapped counties.