The waterways were the first "interstate highway" system, important to transportation. In some places, if none existed, man-made canals were dug, such as Erie Canal all the way across New York State. Choice 'd'.
In the early 19th century, waterways such as rivers and canals were essential for transportation and economic growth in the United States. They allowed efficient movement of goods and facilitated trade between agricultural and manufacturing regions. The chosen answer is D: "They were the easiest means of transportation, used by farmers, herders, and others to get their products to market."
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