text: This crazy jagged border between SF and San Mateo Counties is not correct.  It's basically a straight almost east-west line.  You can read the official definition here:  http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=23138.  Here is an article (apparently there are surveyable boundary markers!): https://www.quora.com/Why-is-San-Franciscos-southern-border-a-straight-line .  You can see the boundary cutting across properties and through houses on the assessors maps available on the SF parcel viewer website: http://propertymap.sfplanning.org/