Article: During the 20th century Valencia remained the third most populous city of Spain as its population tripled, rising from 213,550 inhabitants in 1900 to 739,014 in 2000. Valencia was also third in industrial and economic development; notable milestones include urban expansion of the city in the latter 1800s, the creation of the Banco de Valencia in 1900, construction of the Central and Columbus markets, and the construction of the Gare du Nord railway station, completed in 1921. The new century was marked in Valencia with a major event, the Valencian regional exhibition of 1909 (La Exposición Regional Valenciana de 1909), which emulated the national and universal expositions held in other cities. This production was promoted by the Ateneo Mercantil de Valencia (Mercantile Athenaeum of Valencia), especially by its chairman, Tomás Trénor y Palavicino, and had the support of the Government and the Crown; it was officially inaugurated by King Alfonso XIII himself.

Now answer this question: When was the Valencian regional exhibition held?
1909