This annual weed is scaterred across North America but concentrated in agricultural regions of California and in east-central states from midwest to mid-Atlantic regions (K). It may not have become widespread in eastern North America until after the mid-1800s, when Gray (1864) noted the range as just "Ind. to Kan." It was not recorded in Ky. until 1914, when Gm noted: "common locally along rivers and at the edges of cities elsewhere." It is indeed locally frequent along open riverbanks and larger streams, especially on base-rich fertile soils. It is also typical of grazed farmland, where generally avoided by cattle. A. annua has ancient medicinal use, reducing inflammation and inhibiting varied microbial pathogens; this can be attributed largely to the sesquiterpene lactone "artemisinin" and perhaps synergy with its highly diverse phenolics (e.g. Mueller et al. 2000, Ćavar et al. 2012). Artemisinin has been investigated for potential use in the COVID-19 virus, following initial therapeutic value in Africa and China (Schlagenhauf et al. 2020).