Chelsea Enclave

I have this book called "New York Enclaves" written and illustrated by William H. Hemp and published by Clarkson Potter. A nice opportunity to do some tourism off the beaten track. However I didn't go to see the oldest house in Chelsea as - being I admit a bit chattered by a lot of walking round the blocks (and believe me they are huge) - I misplaced this historic place and I thought it had been replaced by a building under construction opposite 401 West 21st. Ouch !