1979 Map of Portola

To the west, the rugged canyon of the North Fork Yuba River leads to the mining-era settlements of Downieville and Sierra City, while major water projects such as Lake Davis and Frenchman Lake indicate the mid-century infrastructure developments in the region. Transportation routes are prominent, including the Southern Pacific Railroad skirting the eastern edge near Long Valley and the mountain airfields of Beckwourth Airport and Nervino Airport, reflecting the region's role as a vital corridor between the high peaks and the Nevada border.