San Diego Freeway
I-5 through San Diego County follows old US 101. The first section was opened south of downtown San Diego from National City to San Ysidro in the mid 1950’s. It was fully complete through San Diego County by the late 1960’s.
South of the 163, I-5 becomes the Montgomery Freeway. While it was originally completed in the mid 1950’s from National City to San Ysidro, it was completely reconstructed in the early 1970’s to its present state.