California Mission Bells. Click to enlarge. Caltrans photos

The final leg of Caltrans’ Mission Bell project is set for San Rafael to Sonoma, with 40 bells lining Highways 101, 37, 12 and 121.

The state Transportation Commission recently approved $161,000 for the manufacture and installation of the bells.

The state erected the first bells in 1906 along the historic El Camino Real route from San Diego to San Francisco and by 1913 more than 450 bells had been erected one to two miles apart, according to Caltrans. Over the years, many of the bells were removed after being vandalized or damaged and some were stolen, and less than 100 of the original bells remained.

In 1996, Caltrans started to replace the bells and completed the project from Southern California to San Francisco in 2005.

A bell is 18 inches in diameter and is a copy of the original 1906 bell — Caltrans uses the original bell molds to make the new ones.

Caltrans says it installs the bells “based on safety, contractibility, visibility and scenic quality of the site. Spacing between marker locations varies based on existing site conditions and limitations.”

Work is estimated to begin by late summer or early fall.