Which example illustrates an oligopoly market structure in early american history?

What’s the question here?

The embargo act of 1807  was a law passed by the united state congress and signed by president thomas jefferson on december 22,  1807. it prohibited american ships from trading in all foreign ports. in 1806, france passed a law that prohibited trade between neutral parties, like the u.s., and britain.

Dictatorship is the answer you are looking for