Julia Barlow Platt was a comparative embryologist and neurobiologist who was primarily interested in segmentation of the head in vertebrates. She was born on September 14, 1857 in San Francisco, California. Platt grew up in Burlington, Vermont, attended the University of Vermont and began graduate studies at Harvard University. Her nine years as a graduate student were spent on two continents with some of the most influential comparative zoologists of the time. Platt's remarkable scientific accomplishments over a ten year period include a description of axial segmentation currently used in the staging of chick embryos and the first description of a separate anterior head segment in Squalus embryos. Her most controversial study identified ectodermal cells in Necturus embryos that gave rise to head cartilage and dentine, a discovery which was the impetus for the reassessment and modification of the germ layer concept. She was one of the first women to 'matriculate' at a German university and receive a Ph.D. degree. Platt played a pioneer role in opening opportunities for other women who followed her. Platt was one of the first women neuroscientists. Among her contributions, she distinguished dorsolateral placodes, epibranchial placodes, and the first stages of lateral line organs in Necturus, and she described nerve fibers originating in the spinal cord and extending to the notochord in Branchiostoma (= Amphioxus). After receiving a Ph.D. degree in Freiburg, Germany in 1898, Platt was unable to secure a suitable teaching position and, as a result, her scientific career came to an end. She retired to Pacific Grove, California, where she pursued civic duty with the same vigor and energy she had dedicated to scientific research. We provide a sketch of her remarkable life and work as a comparative embryologist, neuroscientist and civic leader.