The taco is the best known and the most popular of Mexican street foods, and the first to be embraced north of the border into the United States. A taco simply is a folded tortilla with some kind of filling. Mexican street taco fillings vary from one region to another. Most tacos are made with corn tortillas, except in the very north of the country where wheat flour tortillas dominate. The tortillas used in Mexican tacos are soft, although the entire taco can be fried, which is called "dorado" (lit. golden). The taco has its origins in the pre-Hispanic period, when other foods were eaten with tortillas, used as a scoop. The modern taco developed in Mexico's rural areas when wives would bring their husbands' meals to the fields wrapped in tortillas. Tacos arrived to the city when stands began to sell foods known to the many rural people who migrated to them in the 20th century. This is especially true for Mexico City, which offers taco specialties from just about every region of the country. The taco bridges social and economic barriers in that everyone in the country eats them, leading it to be called "the most democratic of Mexican foods."
The fillings for tacos vary widely and most taco vendors have a specialty, the most known are al pastor and bistek. There are also tacos for more adventurous people that are filled with beef eyes, brains or tongue. Taco vendors are usually distinguished from other street food vendors by having a large block of wood called a tronco, on which meat and other fillings are minced with a cleaver. Garnishes vary but usually include chopped onion, cilantro, various salsas, grilled green onions, and lime wedges. Many taco varieties are generally available only in the morning or afternoon. Tacos most often found in the morning hours include tacos de canasta and those with barbacoa or cabeza de res (lit. beef head). Tacos de canasta (basket tacos) are the only kind which are not prepared on the spot. They are tortillas with fillings such as potatoes, chorizo sausage, pork rind, beans and picadillo (a spiced ground meat), then steamed and wrapped to keep warm and carried in a basket. Barbacoa is pit-roasted meat. It is most commonly found in the center of the country, where the preferred meat is mutton. In the north of the country, there is a version made with beef. Cabeza de res are made from meat and other parts of a steer, most commonly found in Sonora, the Bajío region and Mexico City. Vendors of these kinds of tacos usually sell out and close by midday. In the afternoon, outside of Mexico City, tacos are generally not available until later in the day. In the late afternoon until well into the night (especially on weekends) other taco stalls open with a different selection. These are principally grilled, fried or steamed meat. One famous night taco in the Mexico City area is tacos al pastor (shepherd style tacos). They are an adaptation of Middle Eastern spit-cooked meat, introduced by Lebanese immigrants. However, the meat is pork and the seasoning is a mild chili pepper, onions and pineapple. Other taco varieties include tacos de guisado, or tacos de cazuela, which are filled with meat or vegetables in a sauce. Fritangas are tacos with fried meat such as sausage. Carnitas is pork cooked in lard flavored with orange rind. It was originally a specialty of Michoacán and Jalisco, but now can be found in most of the center of the country and in other parts of the country as well. The best-known grilled taco is carne asada (grilled meat) which originated in Sonora. It is beef grilled over charcoal, originally mesquite. These are served with grilled green onions and, depending on the region, served with flour or corn tortillas. Fish tacos are a speciality of Baja California and the Pacific coast. They have also become very popular in parts of the United States. Codzitos are small tacos popular in the Yucatán Peninsula, which are fastened with toothpicks and then fried . Flautas, also called taquitos or tacos dorados, are similar to tacos in that they are filled, but they are then rolled and fried. They are served topped with cream, salsa, and vegetables such as lettuce, tomatoes and onions.
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