Yes - you can anchor there. The holding ground was OK last time we anchored, but it is a pretty deep anchorage. The north end of the Salt Pond is closed to anchoring, and is fairly shallow. But just south of that is an anchorage area. If you look at a chart you''ll see it''s 26-32 feet; that''s pretty accurate so you need a long rode. We put out pretty much all of a 200'' rode with 20'' of chain on it, shooting for 7:1 with all of our tackle down and being nervous about making it.
The guy anchored nearest to us, in the exact same boat as ours, probably had 4 or 5 to one out, as we discovered when the wind died then shift 180 degrees.
In re: another post when comparing Champlins vs. the Boat Basin. We never stayed at the Boat Basin, I chickened out on trying to get my boat into the slip they were offering me. However, the last time we did Block Island we anchored, and found it to be much more peaceful than being in a slip there. I suspect that will be our plan there from now one.