The "american system" proposed by henry clay was a plan to:
protect the planters in the south
gain prosperity for the nation through a protective tariff
develop the public schools in the north and south

Gain prosperity for the nation through a protective tariff

Explanation:

Henry Clay defended his economical plan that was called “The American System”.

The main idea of this economical plan was that the federal government would implement a protective tariff, that would protect American manufacturers from foreign competition by increasing the prices of imported goods, this would make the public buy American products and would make the American industries grow.

gain prosperity for the nation through a protective tariff

Explanation:

missouri compromise of 1820 which prohibited slavery