The flag of the state of San Luis Potosí is, like most current Mexican state flags, the coat of arms centred on a white field.
The coat of arms in divided into two fields, a blue one and a gold one. In the centre, the figure of Saint Louis, King of France, which is also on the top of a hill. On the gold field, there's two gold bars and on the blue field there's two silver bars. It is framed by an irregular golden border.
The coat was given by Viceroy Don Francisco Fernández de la Cueva in 1656 to the then town of San Luis Minas del Potosí of the New Spain along with the title of City and it was officially confirmed by King Philip IV in Madrid in 1658.
Proposals for new flag of San Luis Potosí
Design based on the Coat of Arms. By MetamarioMX. 2014.
Civic version of the design based on the Coat of Arms. By MetamarioMX. 2014.
Blue and yellow for night and day. Two gold and two silver bars which represent the state's mining wealth. By kyrgyzzephyr. 2014.
San Luis Potosí flag proposal by Sotajarocho. 2015.
San Luis Potosí flag proposal by Superham1. 2016.