1.Cornelia Clapp (1849–1934) earned both the first and second (from Syracuse and Chicago, respectively) biology doctorate degrees awarded to a woman in the U.S.
2.Alice Brown (1857–1948) studied anatomy at Cornell University and later became a prolific novelist, poet, and playwright who often wrote work with scientific themes.
3.Florence Bascom (1862–1945) was the first woman to earn a Ph.D. from Johns Hopkins University and was also the first woman elected to the Geological Society of America.
4.Annie Jump Cannon (1863–1941) was one of the foremost American astronomers, who focused on variable stars. She was the co-creator of the first serious classification of stars based on temperatures.
5.Mary Agnes Chase (1869–1963) was a grasses expert who often had to fund her own research trips to South America, as it was considered inappropriate for women to do field work.
6.The first woman on the faculty of Harvard Medical School was Dr. Alice Hamilton (1869–1970). She was a foremost expert in occupational health issues.
7.Lillian Moller Gilbreth (1878–1972) was a doctor of psychology, best known for revolutionizing management along with her husband and their famously efficient family of 12 children, chronicled by two of their kids in Cheaper by the Dozen.
8.Emma Perry Carr (1880–1972) was an American spectroscopist who taught chemistry at Mount Holyoke College. She was awarded the American Chemical Society's Francis P. Garvan Medal in 1937.
9.Margaret Harwood (1885–1979) was an astronomer. She was the very first director of the female-run Maria Mitchell Observatory in Nantucket, Mass., a nonprofit science education institute.
10.Libbie Henrietta Hyman (1888–1969) published the classic five-volume reference work, The Invertebrates. She received gold medals from the Linnean Society of London and the American Museum of Natural History.
11.Roger Arliner Young (1889–1964) was a zoologist and biologist and the first African-American woman to receive a doctorate in zoology. During her long career she studied radiation, paramecium, and hydration and dehydration of living cells.
12.Dr. Martha Euphemia Lofton Haynes (1890–1980) was the first African-American woman to receive a Ph.D. in math, and she taught math in Washington, D.C., for 47 years.
13.Botanist Matilda Moldenhauer Brooks (b. 1891) attended Harvard and conducted research along with her husband, Sumner Cushing Brooks. She discovered an antidote for carbon monoxide and cyanide poisoning in the '30s.
14.Marie Agnes Hinrichs (b. 1892) was a zoologist who taught at the University of Chicago, Southern Illinois University, and the University of Illinois. She researched the effects of radiation on developing embryos.
15.Roxana ("Roxy") Judkins Stinchfield Ferris (1895–1978) studied botany at Stanford and went on to edit the classic reference work llustrated Flora of the Pacific States. She collected over 14,000 botanical specimens.
16.Florence Barbara Seibert (1897–1991) was an accomplished biochemist who developed the skin test for tuberculosis.
17.Mildred Adams Fenton (1899–1995) trained in paleontology and geology at the University of Iowa. She and her husband, Carroll Lane Fenton, wrote dozens of science books together.
18.Hattie Elizabeth Alexander (1901–1968) was a pediatrician and microbiologist known for her work in antibiotic resistance and developing a remedy for Haemophilus influenzae. She was the first woman elected president of the American Pediatric Society.
19.Margaret Mead (1901–1978) was a respected cultural anthropologist whose reports on sex in South Pacific and Southeast Asian cultures had a great impact on the sexual revolution. She was posthumously awarded the Presidential Medal of Freedom in 1979.
20.Barbara McClintock (1902–1992), the 1983 Nobel Laureate in Physiology or Medicine (she remains the only woman to receive the prize in that category), was one of the world's most distinguished cytogeneticists throughout her long career.
21.Ruby Hirose (1904–1960) was a Japanese-born American chemist whose infantile paralysis vaccine research was groundbreaking.
22.Regina Flannery Herzfeld (1904–2004) was one of the first female anthropologists in the United States.
23.Bertha Parker Pallan Cody (1907–1978) is known as the first female Native American archaeologist.
24.Mary Knight Dunlap (1910–1992), the founder of the Association for Women Veterinarians.
25.Chien-Shiung Wu (1912–1997) was a Chinese-American physicist who worked on the Manhattan Project and many other experimental physics and radioactive studies. She was the first female president of the American Physical Society.
26.Roxie Collie Laybourne (1912–2003) invented the field of "forensic ornithology," studying fragments of deceased birds to help prevent plane crashes!
27.Mary Blade (1913–1994) was the only woman on the Cooper Union engineering faculty when this photo was taken in 1946. She was also an avid mountain climber.
28.Chemist Mildred Catherine Rebstock (1919–2011) was the first person to synthesize the antibiotic chloromycetin. Read all about her in this fascinating obituary.
29.Mary Sherman Morgan (1921–2004) was a rocket scientist (!). She invented the liquid fuel Hydyne in 1957, which went on to power the U.S.'s Jupiter-C rocket.
30.Mary Alice McWhinnie (1922–1980) was a world-renowned expert on krill who eventually became the first woman to serve as chief scientist at an Antarctic research station.
31.Vera Rubin (b. 1928) is an astronomer known for her work on galaxy rotation rates and dark matter. She has received numerous awards and medals and as of June 9, 2013, has co-authored 114 peer-reviewed research papers.
32.Elizabeth Roemer (b. 1929) was an astronomer who discovered two asteroids and became a professor emerita at the University of Arizona.
33.Joyce Jacobson Kaufman (b. 1929) was a chemist who introduced the concept of "conformational topology." She studied as a special student at Johns Hopkins University, which did not normally admit women until 1970. She won numerous awards and honors.
34.Melba Roy Mouton was a mathematician who graduated from Harvard and later led a group of mathematicians at NASA who were known as "computers" for their intense calculations.