The development of urban center usually occurred where the method of moving goods changed. These locations are called breaks in transportation for obvious reasons: the route is broken into pieces along which you're forced to use different carriers. These could be rail cars, wagons, ships, rafts, or variations of these things.

Every time you change the method of haulage, you have to have people to unload the goods from one form and reload it onto the other form at the break. This results in urbanization because you need warehouses and docks to do this, in turn creating a need for financing and labor. The workers need to be housed and fed, so support industries spring up and eventually enough people are located in the same place either working for the shipping industries or support industries like restaurants, pubs, boardinghouses, or stores, that the place starts looking like a frontier town.

Example: Fort Wayne, IN

Suppose you're a farmer in the area around Fort Wayne, Indiana and you want to send your wheat to New York for resale in Eastern markets. You have two options for doing this.

First, you can send it up the canal to Toledo on the shores of Lake Erie. There, your grain would be transferred to lake ships and sailed over to Buffalo, where it would be offloaded back onto canal boats. These canal boats would take the wheat down to Albany at the other end of the Erie Canal. From Albany, the wheat can be sent down the river to New York - this is an all water route from Fort Wayne to New York.

Second, you could send it down the Wabash and Erie canal and then switch to riverboats or rafts down the Wabash or Ohio Rivers to the Mississippi River. Once at the end of the Mississippi River, your wheat would be offloaded onto sailing ships like clipper ships. These ships would go around the Gulf of Mexico and up the Atlantic Coast to New York. This too is an all water route from Fort Wayne to New York.

Why Switch Boats?

Both of these are all water routes, so they only involve boats. Why do you need to keep switching boats? Isn't the stuff floating on water all the time? Here are some models of boats on the various water routes.

At left is an example of a canal boat used in the 1840s on the Erie Canal. Canal boats had to be narrow enough to fit in the canal because you didn't want to spend a lot of money and time digging really wide canals. These things don't need any stability because they're fitting exactly in a flat canal with no tides and are pulled along by mules.

Here's a schooner on the right used to ship lumber on Lake Michigan. If you used the Great Lakes and Erie Canal route, you'd offload your wheat onto something like this to take it from Toledo to Buffalo on Lake Erie. Obviously, canal boats are not designed to be shipped on a lake, so you really needed to switch to another boat type.

Suppose you wanted to go down to New Orleans. At left is a riverboat you might have used on the Ohio and Mississippi Rivers. Why do you need steam powered propulsion? Because you can't go upstream using just wind power - this is a problem unique to river navigation. Notice how flat the hull is. A steamboat is typically very flat and very wide. If you've ever been to Disneyland, you have probably seen the Mark Twain in New Orleans Square that goes to Tom Sawyer's Island.

Finally, we have a mid-late 19th Century clipper ship used to sail the high seas. What can you say about the hull shape on this thing? No surprise that oceangoing ships were referred to as bottoms. While the cargo on a riverboat is piled on top of the deck, an oceangoing clipper or packet ship stores all the cargo in the holds located in the hull bottom. If you didn't have anything to take (like, if you're returning from somewhere that doesn't make anything you want to take back), then you needed some heavy bulky junk called ballast to throw in the holds to keep the ship balanced. With different sailing conditions on lakes, oceans, and rivers, you have specialized boat designs to navigate each of them. In particular, take note of the hull shape and propulsion (sails, mules, steam).