In diplomacy, a legation was a diplomatic representative office lower than an embassy. Where an embassy was headed by an ambassador, a legation was headed by a Minister. Ambassadors outranked Ministers and had precedence at official events.
Through the 19th century and the early years of the 20th century, most diplomatic missions were legations. An ambassador was considered the personal representative of his monarch, so only a major power that was a monarchy would send an ambassador and establish an embassy. A republic or a smaller monarchy would only send a Minister and establish a legation. Diplomatic reciprocity meant that even a major monarchy would only establish a legation in a republic or a smaller monarchy. For example, in the waning years of the Second French Empire, the North German Confederation had an embassy in Paris, while Bavaria and the United States had legations.
The practice of establishing legations gradually fell from favor as the embassy became the standard form of diplomatic mission. The establishment of the French Third Republic and the continued growth of the United States meant that two of the Great Powers were now republics. The French Republic continued the French Empire's practice of sending and receiving ambassadors. In 1893, the United States followed the French precedent and began sending ambassadors, upgrading its legations to embassies. The last remaining American legations, in Bulgaria and Hungary, were upgraded to embassies in 1966.