During the Ice Age, much of western NY State was under a glacier. These boulders are called "glacial erratics"- rocks that have been broken off, picked up and carried some distance by the ice, then dropped when the glacier melted and receded. The rocks were ground smooth by the dirt and ice mixture- generally, the more rounded the rock, the further it has been carried. In many examples, you'll notice that the rock material is not from anywhere near the local area.
So this is my photographic diary of sorts, a record of giant rocks dropped here and there by the glacier.
Many of these rocks are out in front of older farm houses, leading me to formulate a theory that they were pulled out of the fields so the plows wouldn't be ruined, and placed out front as a manly display of will. Getting such a huge rock dug out, and dragged out front must have been quite some community activity.
All of these rocks are way too big to be "landscape rocks"- they just wouldn't be worth it to be transported far. These are all in the Rochester, NY vicinity.
Here's a big rock behind Huntington Meadow Stables on Salt Rd.. This one appears to be freshly unearthed- note the stained line indicating where it used to be half buried along with the freshly chipped bottom. Webster, NY |
 This nicely-smoothed rock is sitting on the lawn of the Episcopal church at the corner of Rte. 250 and State Rd. Likely unearthed on site during church construction. Webster, NY |
 This rock is on 5 Mile Line Road, just North of Rte. 404 (Ridge Rd.)in the front yard of an old house. Ok, so I forgot my hat! Webster, NY |  Aye Caramba!! This *extremely* big rock is south of Rochester- on W. Bloomfield Rd at the intersection of Thornell Rd. Pittsford, NY |
 I had remembered seeing this rock somewhere, but once I started to specifically look for it to take a picture, it took me a week to find it. It's in front of an old barn on Rte 250, on the east side of the road, a half mile south of Atlantic Avenue. This is a wonderful rock, nicely shaped, and completely made of brownish feldspar- this is another that's clearly traveled quite far as there's no bedrock like this anywhere near this area of the state. Penfield, NY | 
This curiously weathered limestone erratic actually is quite historic, and even has a name... Council Rock. It's on East Avenue at the end of Council Rock Avenue. There is a bronze plaque mounted in the top of the rock that explains that it was dedicated in 1919 to the memory of the Seneca Indians, noting that around this very rock they gathered for councils. Forgot my hat again. Rochester, NY |
I was surprised to run across this one- it's in the back yard of a house on Hard Rd. in Webster, just south of the intersection of Rte. 104. You can see it from the Marriott hotel pool, which is how I discovered it. Webster, NY | 
I'm wearing the hat, trust me! This rock is on Lake Road at Rte 21 in Pultneyville, NY, just off the shoulder of the curve. I believe it was unearthed in the 1990s during road reconstruction and set here. You can clearly see the layering- this rock's come quite a distance- there's no local rock formations with this material. Pultneyville, NY |
This nice rock is in the side yard of a house on Chesham Way. Perhaps it was unearthed when the basement was dug. Nice landscaping! Pittsford, NY |
 This rock is in front of some old farmland on State Rd. Note the mysterious levitation when you touch it! :-) I wonder what the paint's covering up? Webster, NY |