Royal fashion fans, there's a new kid on the block: Princess Leonor. On her 18th birthday today, the future queen of Spain attended a ceremony in Madrid where she pledged allegiance to the Spanish constitution. For the occasion, she wore a striking white pantsuit, which is not only a royal favorite but also has a hidden meaning.

White is symbolic of the women's suffrage movement of the early 1900s. In the U.S., women were first granted the right to vote in 1920, and Spain followed more than decade later in 1931.

Many prominent women have chosen to wear white for historic moments. For instance, Vice President Kamala Harris wore a white pantsuit when she became the first female VP, and ditto Hillary Clinton when she became America's first female presidential nominee. Meanwhile, when Princess Leonor eventually ascends the throne, she will be her country's first queen since Isabella II's reign ended in 1868. Scroll down to see what she wore for the momentous occasion and revisit other royally white pantsuits.