Prairies Province Rocky Mountain Region Vancouverian Province Rocky Mountain Province Madrean Region Great Basin Province Californian Province Sonoran Province Neotropical Kingdom Caribbean Region West Indian Province Paleotropic Kingdom Hawaiian Region Hawaiian Province Some prominent botanists who have studied and published on U.S. flora John Clayton (1694–1773) John Bartram (1699–1777) Carl Linnaeus (1707–1778) Peter Kalm (1716–1779) William Bartram (1739–1823) André Michaux (1746–1802) William Clark (1770–1838) Meriwether Lewis (1774–1809) Frederick Traugott Pursh (1774–1820) Alphonse Louis Pierre Pyramus de Candolle (1778–1841) Constantine Samuel Rafinesque (1783–1840) Thomas Nuttall (1786–1859) John Torrey (1796–1873) George Engelmann (1809–1884) Asa Gray (1810–1888) George Vasey (1822–1893) Sereno Watson (1826–1892) Charles Sprague Sargent (1841–1927) Edward Lee Greene (1843–1915) John Merle Coulter (1851–1928) Marcus Eugene Jones (1852–1934) Liberty Hyde Bailey (1858–1954) Nathaniel Lord Britton (1859–1934) Aven Nelson (1859–1952) Per Axel Rydberg (1860–1931) Alfred Rehder (1863–1949) Albert Spear Hitchcock (1865–1935) Charles Piper (1867–1926) Willis Lynn Jepson (1867–1946) John Kunkel Small (1869–1938) Mary Agnes Chase (1869–1963) Merritt Lyndon Fernald (1873–1950) LeRoy Abrams (1874–1956) Henry Allan Gleason (1882–1975) Paul Carpenter Standley (1884–1963) Edgar Theodore Wherry (1885–1982) Earl Edward Scherff (1886–1966) Emma Lucy Braun (1889–1971) Philip Alexander Munz (1892–1974) Harold St. John (1892–1991) Eric Hultén (1894–1981) Ivan Murray Johnston (1898–1960) Charles Leo Hitchcock (1902–1986) Frederick Joseph Hermann (1906–1987) George Ledyard Stebbins (1906–2000) Elbert Luther Little, Jr. (1907–2004) Julian Alfred Steyermark (1909–1988) Lyman David Benson (1909–1993) Reed Clark Rollins (1911–1998) Rupert Charles Barneby (1911–2000) Albert Ernest Radford (1918–2006) Warren Herbert Wagner (1920–2000) William Alfred Weber (b. 1918) Arthur Cronquist (1919–1992) Ronald Leighton McGregor (born 1919) Carlyle August Luer (born 1922) Robert Kral (born 1926) Stanley Larson Welsh (born 1928) George William Argus (born 1929) Edward Groesbeck Voss (1929–2012) James Lauritz Reveal (1941–2015) Anton Alfred Reznicek (born 1950) Warren Lambert Wagner (born 1950) Barbara Jean Ertter (born 1953) John Thomas Kartesz Further reading Flora of North America North of Mexico. 12+ vols. New York and Oxford, 1993+. The PLANTS Database @ United States Department of Agriculture NatureServe Explorer