Cogdill was first elected to public office in 1975 as a member of the Board of Directors of the Bridgeport Fire Protection District in Mono County.

In 2006, Cogdill was elected to the State Senate to represent the 14th District, which comprised all or a portion of Fresno, Madera, Mariposa, San Joaquin, Stanislaus and Tuolumne Counties.

In the Senate, Cogdill focused his efforts on economic development, strengthening public safety, keeping taxes low, improving air quality, and expanding water supply and storage opportunities.

During his time as Chair of the California State Legislature Rural Caucus, he worked on access to health care and quality education.

This removal was precipitated by Cogdill's agreement to join with Democrats as a member of the "Sacramento Six" to raise vehicle license fees and taxes during the administration of Governor Arnold Schwarzenegger.

In October 2013, Cogdill resigned as Stanislaus County Assessor to become president and CEO of the California Building Industry Association, a post he held until his death.