Take a look at the history of how The Cellar at Hightower came to be, and it's easy to see how New England clam chowder was served instead of the Manhattan version.
When Frank Hightower decided to open a restaurant, he hired iconic cookbook author and chef James Beard as a consultant. Beard happened to have employed young chef John Bennett at a restaurant in Connecticut while Bennett was a student at the Culinary Institute of America.
Beard, for whom the nation's most important culinary awards are named, once wrote “that rather horrendous soup called Manhattan clam chowder ... resembles a vegetable soup that accidentally had some clams dumped into it.” On the James Beard Foundation website, you'll find his recipe with the following preface: James Beard considered this creamy New England-style chowder his “oldest love” — the first soup he ever ate. It can be made with Pacific Coast razor clams or the common littlenecks on the East Coast, and in a pinch, with a can of minced clams.
Here is the recipe made famous at The Cellar at Hightower restaurant, which owed a great debt to both Beard and Bennett.
NEW ENGLAND CLAM CHOWDER
As served at The Cellar at Hightower circa 1964.
8 cups canned or bottled clam broth or clam base and water