Mariana Griswold Van Rensselaer (1851–1934) was one of the premier figures in landscape writing and design at the turn of the twentieth century, a moment when the amateur pursuit of gardening and the increasingly professionalized landscape design field were beginning to diverge. This intellectual biography—the first in-depth study of the versatile critic and author—reveals Van Rensselaer’s vital role in this moment in the history of landscape architecture. Van Rensselaer was one of the new breed of American art and architecture critics, closely examining the nature of her profession and bringing a disciplined scholarship to the craft. She considered herself a professional, leading the effort among women in the Gilded Age to claim the titles of artist, architect, critic, historian, and journalist. Thanks to the resources of her wealthy mercantile family, she had been given a sophisticated European education almost unheard of for a woman of her time. Her close relationship with Frederick Law Olmsted influenced her ideas on landscape gardening, and her interest in botany and geology shaped the ideas upon which her philosophy and art criticism were based. She also studied the works of Charles Darwin, Alexander von Humboldt, Henry David Thoreau, and many other nineteenth-century scientists and nature writers, which influenced her general belief in the relationship between science and the imagination. Her cosmopolitan education and elevated social status gave her, much like her contemporary Edith Wharton, access to the homes and gardens of the upper classes. This allowed her to mingle with authors, artists, and affluent patrons of the arts and enabled her to write with familiarity about architecture and landscape design. Identifying over 330 previously unattributed editorials and unsigned articles authored by Van Rensselaer in the influential journal Garden and Forest—for which she was the sole female editorial voice—Judith Major offers insight into her ideas about the importance of botanical nomenclature, the similarities between landscape gardening and idealist painting, design in nature, and many other significant topics. Major’s critical examination of Van Rensselaer’s life and writings—which also includes selections from her correspondence—details not only her influential role in the creation of landscape architecture as a discipline but also her contribution to a broader public understanding of the arts in America.