In May 1911, President Porfirio Diaz was expelled from Mexico and Francisco Madero, the son of a rich landowner, assumed the presidency. In February 1913, General Victoriano Huerta instigated a revolution and the people of Mexico City rose up against Madero. On February 22nd Madero was assassinated and General Huerta proclaimed himself as the provisional president, until his official election took place on October 26, 1913.
Among Madero's best friends and supporters were Maytorena, Governor of Sonora, and Carranza, the Governor of Chihuahua. When Huerta was elected President, Carranza and a few hundred of his followers went to Sonora and he declared himself Chief of the Revolutionary Army. The State of Sonora revolted and declared itself free and independent of Huerta and started a civil war by driving the Mexican Federales out of the State of Sonora.
Prior to the revolution, the State of Sonora had the usual supply of government stamps on hand, but these were soon exhausted and it was necessary to provide new stamps for postal and revenue use.
The first of these stamps, "The White Issues," were issued in May 1913. The inscription on these stamps "Estado Libre y Soberano de Sonora" is translated as "Free and Sovereign State of Sonora." These stamps were embossed with the word "Constitucional," used as a control mark. However, they were hand struck, a slow a process, and the next issues of Sonora were overprinted with a green seal. I do not have an example of the White - a few with the green seal updated.
In 1916, the overprint "G. P. DE M." ( Gobierno Proviorio de Mexico)- "Provisional Government of Mexico"- was used on eleven stamps of the 1910 Independence issue. The overprint is known as the "Corbata". Visually, I really like this Corbata overprint. Close up of Scott 572. Also In 1916, a new surcharge overprint, known as the "Barril", was applied on some of the 1910 Independence issues. The "Barril" can be found in brown, blue, green, and red.