Gumbo (Gombo) is a stew popular in the U.S. state of Louisiana, and is the official state cuisine. Gumbo consists primarily of a strongly-flavored stock, meat or shellfish, a thickener, and what Louisianians call the "Holy Trinity" of vegetables, namely celery, bell peppers, and onions. Gumbo is often categorized by the type of thickener used, whether okra or filé powder (dried and ground sassafras leaves). The dish derived its name from Louisiana French, which may have derived the name from a source such as the Choctaw word for filé (kombo). Gumbo can be made with or without okra or filé powder. The preferred method in the historical New Orleans variation is with a French dark roux. The flavor of the dish has its origins in many cultures. Creole gumbo generally contains shellfish, and a dark roux, filé, or both. Tomatoes are traditionally found in Creole gumbo and frequently appear in New Orleans cuisine. Cajun gumbo is generally based on a dark roux and is made with shellfish or fowl. Sausage or ham is often added to gumbos of either variety. After the base is prepared, vegetables are cooked down, and then meat is added. The dish simmers for a minimum of three hours, with shellfish and some spices added near the end. If desired, filé powder is added after the pot is removed from heat. Gumbo is traditionally served over rice. A third, lesser-known variety, the meatless gumbo z'herbes, is essentially a gumbo of slow-cooked greens. The dish combines ingredients and culinary practices of several cultures, including African, French, Spanish, German, and Choctaw. Gumbo may have been based on traditional native dishes, or may be a derivation of the French dish bouillabaisse, or Choctaw stew, but most likely all of these dishes contributed to the original recipe. It was first described in 1802, and was listed in various cookbooks in the latter half of the 19th century. The dish gained more widespread popularity in the 1970s, after the United States Senate dining room added it to the menu in honor of Louisiana Senator Allen Ellender. The popularity of chef Paul Prudhomme in the 1980s spurred further interest in the dish.