Complex sentence: National parks must be established by an act of the United States Congress, and the first national park, Yellowstone, was signed into law by President Ulysses S. Grant in 1872, followed by Sequoia and Yosemite in 1890.
Split into simpler sentences: National parks must be established by an act of the United States Congress. The first national park, Yellowstone, was signed into law by President Ulysses S. Grant in 1872, followed by Sequoia and Yosemite in 1890.