What was a significant economic institution challenged by President Andrew Jackson during his presidency?

The significant economic institution challenged by President Andrew Jackson during his presidency was the Second Bank of the United States. Jackson believed that the Bank represented a corrupt and elitist institution that wielded too much power over the economy and was detrimental to the interests of the common man. He viewed it as an entity that favored the wealthy and perpetuated class distinctions, leading him to take strong actions against it, including the veto of the recharter bill and the subsequent removal of federal deposits. This struggle was pivotal in shaping the U.S. banking system and economic policies, leading to the rise of state-chartered banks and what is often referred to as the "Bank War."

The other options represent institutions that either did not exist during Jackson's presidency or were not primary targets of his economic policies. State banks were alternatives to the national bank but were not specifically challenged in the same way. The Federal Reserve was established much later, in 1913, while credit unions emerged even later in the 20th century. Thus, the Second Bank of the United States stands out as the focal point of Jackson's economic challenges.