Del Mar Bluffs Stabilization Project 4 (DMB4) is located along 1.6 miles of NCTD railroad right-of-way (ROW) in Del Mar, CA. The study was performed to determine the presence or absence of prehistoric and historic resources within the project boundaries and make significance recommendations (National Register of Historic Places (NRHP) and California Register of Historic Resources (CRHR)). The study consisted of a record search, a Sacred Lands File Search through the Native American Heritage Commission, information requests from local Native American tribal representatives, an intensive pedestrian survey of the project area, and historic research regarding historic-era structures in the project area. Architectural historian Doug Mengers managed the cultural resources study for historic structures and archaeological sites within the ROW. He met with SANDAG project personnel, authored the final report, created all associated GIS maps and made recommendations for resource mitigation measures.