The exact identity of the Viola shown on this page has been the subject of considerable debate.  Intermountain Flora indicates that David Douglas first discovered a yellow Viola near the Columbia River in the early 1800s and Douglas named it Viola glareosa in Hooker's Flora Boreali-Americana. (Click the title to read.)  But Hooker also published Viola nuttallii variety major in Flora Boreali-Americana, following Frederick Pursh's nomenclature from 1814 when Pursh named and described Viola nuttallii from a specimen collected "on the banks of the Missouri" in 1811 by Thomas Nuttall. (Click for biographical information about Nuttall).

In 1899, Aven Nelson examined the specimens and named them V. vallicola, a name confirmed by Dorothy Fabijan in 1987 and accepted by numerous authors, including John Kartesz, the ultimate authority for names on this web site.  (See Kartesz's range maps below.)

Stanley Welsh author of A Utah Flora, points out that in the "strict sense" Viola nuttallii is found almost exclusively east of the Rockies, but he does not accept this "strict sense" and indicates that only V. nuttallii exists in Utah. 

William Weber indicates that both V. nuttallii and V. vallicola exist in western Colorado and that they are distinguished from each other as follows:

V. nuttallii: less that 5 centimeters tall with narrow leaf blades at least 3 times as long as wide and gradually narrowing to the petiole.  Low elevations.

V. vallicola: can be as small as V. nuttallii but may be larger.  Leaf blades broader and often much larger, abruptly narrowed to the petiole.  Leaves less than 5 centimeters long and somewhat truncate at the base (Otherwise like V. nuttallii).  At higher elevations than V. nuttallii.