This area, also known as Penn’s Grove and Penn Grove, was first settled in 1852, though the exact origin of its name is uncertain. With the completion of the San Francisco and North Pacific Coast Railroad in 1870, a town developed where the railroad crossed Main Street, then the main Santa Rosa-Petaluma road. From here the railroad carried thousands of cobblestones, quarried nearby, to Petaluma, where they were loaded onto barges and shipped to San Francisco. After 1900, Penngrove developed into the second largest egg and poultry producing area in the county.