The following was the email I sent and received, the section highlighted in red is the part of interest. I'll do a little digging and see if I and find it on a map.
Allen <><
Hi Larry,
Would you do me a favor? I need good directions to that little cannon park in Nassau County, I have some people doing research on breech loading artillery, and I remember there was a civil war screw breech cannon cemented into one of the monuments. They want to get photos and measurements, This is something that has not been on the radar before and is causing some excitement, as there are few known cannon of this type in existence, it may be one produced by the confederates in a rail yard down in Georgia.
Thanks,
Allen <><
Hi Allen,
We did a bunch of driving around that day, long ago. We looked at cannon in Rockville Centre (by the municiple building - Clinton Street, north of the LIRR station, a block.) We looked at cannon in Freeport, on an traffic island by Sunrise Hway (rt. 27) and over by the Freeport LIRR station (another traffic island, near the taxi stand).
I think you are referring to the cannons in the park in East Rockaway (south of Lynbrook, off the Sunrise Hwy.) That had the old grist mill in the park also. That park is on the east side of Atlantic Ave (coming south out of Lynbrook - on the east side. This is before the avenue ends at Main street in East Rockaway village ... be advised Main St. (east-west) becomes another Atlantic Ave, when it comes into Oceanside. That park is in East Rockaway.
I no longer have maps of Nassau County or that general area. I think the building there was the village hall, but am not sure. Been a VERY long time since I was there.
Hope that helps ... and they better be there when I visit again in a decade or two ... LOL.
Larry