Old Saint Hilary's Open Space Preserve is a county park located in Marin County, California. It is 122 acres large and is connected to the Tiburon Uplands, which is 24 acres. The preserve was created by several local initiatives in the 90’s to save the land from development.[1] It is a popular place for hikers because of its views and other features.[2] There have been initiatives to expand the preserve, such as one that passed in 2022 that aims to connect it with undeveloped, but formerly privately owned land on its perimeter.[3]