Philadelphia's proximity to the Schuylkill and the Delaware River allowed its mills to easily load goods onto ships and sell the stuff somewhere else - a huge business advantage in the 1820s.

But here's the problem with tying your prosperity to the rivers:

Ice.

At the time, Philadelphia wasn't a national manufacturing center - it was the national manufacturing center, the "Workshop of the World" long before anyone hung that tag on the city. It produced everything from rough sails to fine glasswork, traded with everyone from Cuba to China.

Rice, cotton, tobacco and horsehides, coffee from Brazil, toys from Germany, linen from Ireland - all of it came into Philadelphia from the rivers.

But in the winter of 1831-32, the city's ports were shut by ice so thick it supported horses and sleighs. A few years later, in 1835-36, the Delaware iced again, stopping shipping for more than two months. People skated on the river, and enterprising businessmen set up booths on the ice to sell refreshments.

In February people held an ox roast on the ice, near Smith's Island. Not until March could ships move between Chester and Philadelphia.

The next winter the Delaware froze again - and people were weary of it. The ice might be fun for skaters, but not for laborers who were tossed out of work by the halt in commerce, or for merchants who saw their buyers go north to New York.

That year, the city government allocated $70,000 to build a vessel they hoped would lessen the misery:

An ice boat.