[4] The word calabazas is found on a diseño of part of the Agua Caliente land grant in 1840, just west of the Arroyo de los Guilicos.

One of Sonoma County's oldest stone arch bridges, from the year 1915, spans Calabazas Creek near Dunbar School.

[7] In 2004, the Sonoma County Agricultural Preservation and Open Space District acquired 1,290 acres (5.2 km2) in this watershed for conservation purposes, and completed a Resource Management Plan in 2016.

In the Miocene era, precipitated by the combination of tectonic movement due to the seismically active environment and the presence of magma not far below the Earth's surface, a massive period of uplift ensued.

Calabazas Creek originates about 4 mi (6 km) northeast of the town of Glen Ellen, California, just north of Trinity Road, at the top of Nunns Canyon.

Proceeding upstream for the next mile, there is continuous close viewing of the creek, since Nunns Canyon Road runs near the top of the west stream banks.

Some of the steeply sloped forested areas are characterized as good examples of such woodlands, testifying to the absence of historic grazing or other agriculture.