Much like the community it serves, the Ironhouse Sanitary District has a long and storied history. Born in 1945, ISD blossomed from a small utility serving a rural town of a few hundred people to a thriving district that today provides for the sanitary services of nearly 30,000 customers. Following is a timeline highlighting important moments in ISD's evolution.
- July 2, 1945 — Oakley property owners present a petition to the Contra Costa County Board of Supervisors to begin the process of forming a sanitary district.
- Aug. 21, 1945 — Oakley approves a ballot measure calling for the formation of the Oakley Sanitary District by a unanimous 112-0 vote.
- August 1945 — The district's first board of directors is elected.
- February 1946 — On a 122-2 vote, district property owners authorize a $30,000 bond for construction of a sewer line.
- 1964 — Concerned property owners in the Hotchkiss Tract area launch efforts to replace their overburdened septic tanks with a sewer system.
- November 21, 1967 — County Sanitation District No. 15 Citizen's Advisory Committee is created in response to the Hotchkiss residents. A joint powers agreement (JPA) is later established with the Oakley Sanitary District.
- 1978 — Sewer system becomes operational in Sanitary District 15 boundaries.
- March 29, 1977 — JPA is signed between Oakley and Bethel Island, establishing the Oakley-Bethel Island Wastewater Management Authority. OBIWMA's board consists of two representatives each from Oakley Sanitary District and Sanitation District 15, plus one member at large.
- January 31, 1992 — Oakley Sanitary District annexes Bethel Island, the JPA is dissolved, and the district merges with OBIWMA and Sanitary District 15.
- Iron House School February 1, 1992 — The new entity is renamed the Ironhouse Sanitary District (ISD), borrowing its name from a rural schoolhouse that once served the area of Oakley and Hotchkiss Tract. Two board members from the Bethel Island area are added.
- 1994 — ISD purchases 3,600 acres on Jersey Island for future disposal needs. New administration offices are constructed on Walnut Meadows Drive in Oakley.
- 1996-1997 — Provided additional aeration as part of interim expansion of the existing treatment facility to accommodate residential growth.
- October 15, 2011 — ISD opens its new Water Recycling Facility, a $59 million state-of-the-art plant that treats wastewater to standards that exceed state environmental requirements and provides expansion capacity to serve the district's customers for decades to come. The plant receives the California Association of Sanitation Agencies award for technological achievement.
- August 2013 — The district receives the California Association of Sanitation Agencies award for outstanding public outreach.