Until the Vienna Convention on Diplomatic Relations, there were various types of diplomatic missions. Legations were the most frequent type and were the physical representation of a government vis-à-vis the receiving State.
The heads of these missions held the title of ministers in a conventional way, although the full name was the Envoy Extraordinary and Minister Plenipotentiary. The origin of the title corresponds to the particular circumstances in which the diplomatic office was carried out, since the communications were very slow, it had the capacity to act with full powers on a particular issue.
Embassies were reserved for special occasions and to represent the state at very specific times or places. The chief of mission, however, had to follow his instructions to the letter
With the improvement in communications and the proliferation of negotiations between many States, legations fell into disuse and were removed by the Convention. The case of Mexico
This is the position with which the Mexican government accredited its representatives abroad throughout the nineteenth century and part of the twentieth. Ministers settled in legations close to foreign governments. The first to be sent, counting from the consummation of the Independence of Mexico was Jose Maria Zozaya, accredited in 1822 before the government of the United States. This was also the first legation that raised its rank to embassy in 1898, being Matías Romero the first Ambassador of Mexico abroad.
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