\in 1861, ordered the union navy to blockade the rivers, canals, and ocean ports of the south.

The correct answer is Abraham Lincoln

This was at the beginning of the civil war. The south relied on foreigners to get their necessary goods like manufactured products or weaponry or similar things and they also relied on the ports to get their politicians to Europe and try to get recognized as an independent country. Lincoln blocked their ports with Northern ships in order to prevent them from doing this.

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