What do we call vast grasslands owned by the federal government?

The term that best describes vast grasslands owned by the federal government is "Open Range." This concept refers to large, unfenced areas where livestock can graze freely on public lands. Historically, the Open Range developed in the western United States as ranchers took advantage of the expansive grasslands for grazing cattle. It played a significant role during the cattle drive era in the late 19th century, allowing ranchers to raise livestock without the need for individual fencing of land.

While "Public Domain" typically refers to lands that are owned by the government and available for public use, it encompasses a broader range of lands beyond just grasslands. "Common Land" usually refers to land shared by a community rather than federal ownership. "Federal Reserve" usually pertains to the central banking system of the United States and doesn't relate to land ownership. Thus, "Open Range" accurately captures the specific nature of vast grasslands owned by the federal government used for grazing.