Medical care has come a long way since the days when doctors and pharmacists regularly “bled” patients, often by using live leeches, to cure diseases. Innovations such as antibiotics, which were discovered in 1928 by Sir Alexander Fleming at St. Mary’s Hospital in London, and anesthesia, which was first used to treat a patient in 1846 by William T. G. Morton and John Collins Warren at Massachusetts General Hospital in Boston, have saved millions of lives worldwide.

While healthcare innovations like these made by men are remarkable, we often forget to think about the many extraordinary women who have made an impact in the healthcare industry, contributions that are all the more impressive when you consider that women were often discouraged from, and in many places not allowed to, attend colleges, universities or medical schools.

Read on to learn about four notable women whose work has made a major impact on healthcare, and in many cases whose influence is still felt in doctor’s offices and hospitals today.

Florence Nightingale: Founder of Modern Nursing

Often considered a pioneer in the field, Florence Nightingale had a major impact on nursing. Born in England in 1820, Nightingale was a social reformer and trained statistician who began her career by organizing nursing care for wounded soldiers during the Crimean War. She founded a nursing school in 1860 at St. Thomas Hospital in London, establishing one of the first intuitions where women interested in nursing could receive formal training. Most nurses at the time were self-taught or learned the trade by apprenticing with more experienced nurses. Standardizing nurse training and making it available to more women increased the number of available nurses, making healthcare available to more people.

Clara Barton: Founder of the American Red Cross

Born in Oxford, Massachusetts, in 1821, Clara Barton was a self-taught hospital nurse who cared for wounded Union soldiers during the American Civil War. She was also a teacher and humanitarian who helped distribute medical supplies to Union troops. After the war, in 1869, Barton traveled to Europe. In Switzerland, she learned about the International Red Cross, which was founded in 1862 in Geneva. When she returned to the United States, Barton pushed for the founding of an American Red Cross by writing leaflets, giving talks, and meeting with President Rutherford B. Hayes. The American Association of the Red Cross was formed in May 1881. Barton was elected its first president the following month.

Marie Curie: Inventor of Mobile Radiography Units

Marie Curie was born in 1867 in Warsaw, Poland, and later became a naturalized French citizen. Perhaps most well known for her discovery of the elements radon and polonium, Curie was a professor at the University of Paris, where she also earned several degrees. Curie was the first woman to win a Nobel Prize and is the first person, and remains the only woman, who has won twice. She is today also the only person to have won a Nobel Prize in two different sciences (Physics, 1903 and Chemistry, 1911).

During World War I, Curie set up 20 mobile radiology vehicles (known as “Petite Curies”) and more than 200 radiology centers at battlefield hospitals to assist the surgeons who were treating wounded soldiers. The ability to take x-rays on site likely saved thousands of lives, and helped thousands more soldiers avoid having limbs amputated. A version of Curie’s mobile x-ray unit is still used today.

Gertrude Belle Elion: Developer of Purinethol, the First Major Drug to Fight Leukemia

Born in New York City in 1918, Gertrude Belle Elion was a pharmacologist and chemist who developed several pioneering drugs that are still used today to treat a variety of diseases. Elion graduated from Hunter College, in 1937, with a degree in Chemistry, where she had a full scholarship. After being rejected for financial aid to enroll in a masters degree program because of her gender, Elion briefly attended secretarial school and worked as food quality inspector at a supermarket, before eventually enrolling in New York University.

Her most famous discovery, the drug Purinethol, was the first major drug used to treat Leukemia. Other drugs developed by Elion include Azathioprine, Allopurinol, Pyrimethamine, Trimethoprim, Acyclovir and Nelarabine which are used to treat several serious conditions including malaria, gout, meningitis, bacterial infections, organ transplant rejections, herpes and several forms of cancer. Elion also contributed to the development of azidothymidine (AZT), which was the first drug treatment for HIV/AIDS.

Elion won the Nobel Prize in Physiology or Medicine in 1988 for her work in developing drug treatments for a variety of diseases.