The Usami Stone Quarry was the second half of my day exploring the former Edo Castle stone quarries in Izu. Usami is much less dramatic than Ookawa, but it is much more tourist friendly. There is a small park in front of the station with some stones that were found in the same area of town during construction projects and there are a few other significant stones placed around the town for you to walk to. There are also a couple hiking courses that take you to these and up into the nearby mountains for the actual stone cutting sites. There are far fewer remnants here compared to Ookawa but it is a worthwhile trip.
The very large stone above has a mark that indicates it belongs to the Matsudaira of Ehime. At one time 3000 ships were making the trip from Izu to Edo twice a month. For some of the biggest corner stones, they could only fit 2 in each ship. Sometimes these ships were damaged or the stones were dropped in transit so there are also many stones on the ocean floor along the coast. I have seen some pictures of them, but I probably won't be visiting any.
The link below has a map of the Usami hiking courses. I only had time for the Nakoyama course, but I will try another someday. The small yellow circles with 刻 in the middle are the locations of stones that have the owner's mark carved into them. If you go on any of these courses, watch the signs carefully. In some places the trails are very poorly marked and they are not well travelled so it is easy to miss where you should go. Watch for ribbons or paint marks on the trees and keep an eye on the track that seems to have fewer trees or undergrowth. In the three hours or so I was on the mountain trail I didn't see even one person despite it being a fabulous vacation day during Golden Week.