25,000 Years Ago

Yokosuka City's web-site states that the earliest human footprint discovered in the Miura Peninsula was from 25,000 years ago.  So, the land upon which Yokosuka exists is truly ancient, in terms of people living and dying on it.

Flash-forward to 300-600 AD, or so (I'm still leaning about this), and it was a time when agriculture (rice farming) was becoming wide-spread, and replacing the hunter-gathering livelihoods of the "Jomon" era.

Those family groups who had good luck with harvests and invested & concentrated their wealth, also developed political powers.  When their top members died, those family groups (or tribal leaders) were able to convince (coerce?) others to join-together to build large burial mounds called: "Kofun" ( 古墳 ) --- and the most famous Kofun are located elsewhere in Japan and associated with the Imperial family.

But, there are also Kofun located in Yokosuka.  One of them is at Otsuka-Dai (up the hill from Keikyu Kita-Kurihama station), and has been turned into a small park.

Japanese link about the Otsuka-Dai Kofun park.