The wild ones in your area are a different species than most of the named cultivars.
Black Beauty, Brunette, Atropurpurea, Black Negligee, White Pearl, etc. are seedling selections of Cimicifuga(Actaea) simplex, var. simplex, from NE Asia(N Japan, Korea, China, Russia(Kamchatka)* and they bloom later in the year than our native species, Cimicifuga(Actaea) racemosa.

As far as I have been able to determine, there are no named cultivars of our native species, but the plants and seed are available from various sources. Often listed under their several common names; Black Cohosh, Baneberry, Black Baneberry, Bugbane, Black Bugbane, Black Snakeroot, etc.

One source that sells bareroot plants, in bundles of 5, at a very reasonable price, is linked below.

The Genus name, Cimicifuga, was recently changed to Actaea, so you may find it listed both ways.

*
Ref. The Explorer's Garden, Daniel J. Hinkley, Timber Press, 1999 (Chapter 3, Pg. 72)

Here is a link that might be useful: Viola Valley Wildflowers

You are looking at two different species. Actaea (formerly Cimicifuga) racemosa is most likely the native bugbane you are seeing, although could also be A. americana - the two species are pretty well muddled. It blooms mid summer, generally July or August. Actaea simplex and hybrids are commonly known as autumn bugbane or snakeroot and bloom later, usually around September or October. These selections include the dark foliaged forms like 'Brunette', 'Black Negligee', 'James Compton', etc. , collectively known as the 'Atropurpurea Group'. These are sometimes sold as Cimicifuga ramosa, however that taxonomy is invalid.

All in all, the taxonomy of this genus is pretty messed up when researching or tracking down specific plants :-) Selections of each are widely mislabeled in the trade. But very generally, Actaea or Cimicifuga racemosa will have early blooms, green foliage and unpleasantly scented flowers while A. or C. simplex/ramosa will have later blooms, often deep wine or burgundy foliage and honey-scented flowers.

Are you confused enough now?? :-)

Thanks for the responses. I knew that Cimicifuga was now Actea and it was also known as Bugbane, etc. but did not realize that what I'd bought was not C. racemosa.

Maybe I need to make friends with the neighbor who has a beautiful stand of it in the summer.