Rau complemented his landscape and travel photographs with event photographs. Notable events he covered included the Spanish-American War in 1898, the Klondike Gold Rush in the late 1890s, the funeral of President William McKinley in 1901, the eruption of Mount Pelée in 1902, the funeral of Admiral William T. Sampson in 1902, the America's Cup race of 1903, the Great Baltimore Fire of 1904, the inauguration of President Theodore Roosevelt in 1905, and the arrival of the RMS Olympic in New York Harbor in 1911. He was also the official photographer for the St. Louis World's Fair in 1904 and the Lewis and Clark Centennial Exposition in Portland the following year.