Trillium erectum, commonly called the red trillium, is a wide-ranging species of flowering plant in eastern North America. Trillium erectum var. album, sometimes called the white-flowered red trillium, is a white-petaled form of Trillium erectum, but beyond that there is little agreement.

Plants of the World Online (POWO) claims that T. erectum var. album ranges across three Canadian provinces and 22 U.S. states. The list of provinces and states in POWO is taken verbatim from the Flora of North America (FNA), which POWO cites as an authority. For a long time I subscribed to the treatment of Trillium erectum var. album in FNA but I now believe the variety is confined to the southern Appalachian Mountains. The white-petaled forms outside of this region are best thought of as (nameless) forms of T. erectum. The following article explains this in more detail:

• White-flowered red trillium (Dec 2021)