What are some key moments in the early nineteenth century when federal authority clashed with state authority?

There were many clashes between federal and state authority in the early 1800s (if by that we mean the period before 1850). Here are a few examples:

• A debate over a federal appropriations bill in 1817 that would have set aside funds for internal improvements like roads and canals. The construction of these things was held by some to be a power reserved to the states, and many Republicans opposed it on these grounds. President James Madison vetoed it though he supported the idea of internal improvements. He thought that a Constitutional amendment needed to be passed to grant such a power to Congress, however.


• The issue of federal laws and state laws that emerged from interstate navigation. This was a longstanding issue that came to its conclusion in the Supreme Court's decision in Gibbons v. Ogden (1824). This case involved contradictory monopolies, or charters, granted by the state of New York and the federal government. The Supreme Court sided with the federal government, which alone has the power to regulate interstate commerce according to the Constitution.


• The Nullification Crisis of 1832. This crisis stemmed from several federal "protective" tariffs that benefited Northern manufacturers more than Southern planters. The state of South Carolina, with John C. Calhoun as its spokesman, claimed the right to "nullify" the tariff along with any other legislation that was damaging to its interests, and suggested that they could leave the Union if this right was not respected. A compromise was reached wherein tariffs would be lowered over the next decade, but the event was the most significant, and most dangerous clash of federal and state authority in the early nineteenth century. 

Of course, as time went on, the sectional tensions between North and South became more severe, and many more clashes between federal and state authority ensued.