The environmental history of the United States is often framed as a contest between those who want to protect remote wilderness areas and those who want to develop resources such as timber or water. This dissertation turns toward wild gardens, as an idea and as a set of built sites, to understand an alternate lineage of environmental thought that prioritizes the cultivation of close-to-home wildness. Bringing together the fields of environmental history and landscape history, this dissertation finds that for the past 150 years there have been historical actors committed to planting and cultivating wildness in gardens and parks. By the turn of the twentieth century a compelling environmental politics of wild gardens had developed within the context of Progressive Era social reforms. In the 1910s and 1920s, the wild garden movement offered a vision of how ecological science, social responsibility, plant aesthetics, and species preservation could intermingle with daily life in cities and suburbs—a set of ideas and practices with relevance to contemporary crises related to climate change, biodiversity loss, and social injustice. This movement lost its momentum by the 1930s, and this shift away from wild gardens, marked by the rise of ecological preserves and a hesitation to embrace human intervention within spaces considered part of the natural world, restricted the possibilities of popular environmental thought for much of the twentieth century. By the early years of the twenty-first century, wild gardens returned to the United States, gaining popularity within a broader cultural shift that recognized and embraced the idea that humans lived entangled within the natural world. A willingness to embrace the opportunities of human intervention within wildness reappeared within American environmental thought. This revived wild garden movement, appearing in prominent public and private spaces, is still developing, with practices and sites created by both professional designers and committed citizens. By turning to wild gardens at the turn of the twentieth century, there are lessons to learn that can support this movement over the next 50 years.