Roxbury Puddingstone is the bedrock of Jamaica Plain. Anywhere you see a rock outcrop, you can expect it to be of the famous conglomerate. Churches, walls and foundations have been made of it throughout the community, with much of it probably coming from either the site or very nearby. In looking for an online source of information on our state rock, I came upon this entry from an old book. For anyone with questions about Roxbury Puddingstone, I think that's the best you'll get without going to a good library.
Just to clarify: Roxbury Puddingstone may be glacial in origin, but it is not the product of the (relatively) recent ice ages that shaped the surface of modern Massachusetts. This is some very old rock - recent sources date it to 500 million years - that's Precambrian for you geologists and paleontologists.