Siskiyou Gardens, Parks and Greenway Association represents the coming together of several groups concerned with public green space in the city of Yreka. Its formal history dates to 2003 when a Ford Family Foundation Leadership Institute team adopted the development of Greenhorn Park as its project. A year later, the city of Yreka purchased additional land to create a 400-acre preserve around Greenhorn Reservoir and a mile of Greenhorn Creek.

Public meetings were held to develop the park as a community asset, and by 2005 the Greenhorn Park Development Initiative’s garden committee had matured into the Siskiyou Arboretum and Gardens Project. The Arboretum built a nursery on city land and laid plans for promoting the use of native plants in the park, in residential gardens and in local restoration projects. Community vegetable gardens and children’s educational gardens were also a part of this vision.

The gardens began to be planted at the park and within the community, and by 2009 the Arboretum incorporated as a non-profit educational organization. The Arboretum’s success made it a nexus for partnership with the original Greenhorn Park advocates and with the Yreka Creek committee, an organization with a long history of developing Yreka Creek Greenway in collaboration with the city. In October of 2009, the Arboretum formally reorganized into an umbrella group with the name Siskiyou Gardens, Parks and Greenway Association.