Mardi Gras in the United States is not observed nationally across the country, however a number of cities and regions in the U.S. have notable Carnival celebrations.
 Most trace their Mardi Gras celebrations to French, Spanish, and other colonial influences on the settlements over their history.
 The earliest Carnival celebration in North America occurred at a place on the west bank of the Mississippi river about 60 miles (96.6 kilometers) downriver from where New Orleans is today; this Mardi Gras on the 3rd of March 1699 and in honor of this holiday, Iberville named the spot Point du Mardi Gras (French: "Mardi Gras Point").
 The earliest organized Carnival celebrations occurred in Mobile, Biloxi, New Orleans, and Pensacola, which have each developed separate traditions.
 In addition, modern activities generally vary from city to city across the U.S.
The Mardi Gras Mystery is the 81st book in the Nancy Drew series.
 Set in New Orleans at Mardi Gras, it concerns a mysterious art theft.
Nancy Drew, Girl Detective replaced the long-running Nancy Drew mysteries series, which began in 1930.
 This new series is written in first person narration, from Nancy's point of view, and features updated and overhauled versions of the main Nancy Drew characters.
 Nancy Drew in this version is a less than perfect teenage girl prone to forgetfulness, an object of jokes, and interested in other subjects over mysteries.
 Bess Marvin has gained skills in mechanics and computers and is no longer slightly overweight, and described as fashionable and trendy.
 George Fayne has become moody and sloppily dressed in this series, always more interested in tech and sarcastic retorts than solving mysteries.
 New secondary characters are introduced to populate River Heights and appear over multiple books, adding a framework to Nancy's world.
 Bess and George also gain siblings and family members with careers.
 Though this series has many improvements over the "Nancy Drew Mystery Stories", the drastic change in the main characters' personalities was hard for many readers to accept.
 In 2013 "Nancy Drew, Girl Detective" was replaced with the "Nancy Drew Diaries" series.
Mardi Gras World (also known as Blaine Kern's Mardi Gras World, MGW) is a tourist attraction located in New Orleans.
 Guests tour the 300,000 square foot working warehouse where floats are made for Mardi Gras parades in New Orleans.
 Mardi Gras World is located along the Mississippi River, next to the Morial Convention Center.
 Their events venue, the River City Complex, also hosts festivals, weddings, private parties and corporate events.
Mardi Gras Park is a municipal park in downtown Mobile, Alabama, USA.
 The park is bounded by Government Street to the north, Royal Street to the east, Church Street to the south, and St. Emanuel Street to the west.
 The park opened in November 2016.
 It is located on the site of the old Mobile County Courthouse.
 The park features statues representing the Mardi Gras tradition of the City, including Mardi Gras royalty, jesters, and Joe Cain (as his alter ego, Chief Slacabamorinico), who is largely credited with initiating the modern way of observing Mardi Gras and its celebrations in the city following the Civil War.
The Courir de Mardi Gras (] ] ) is a traditional Mardi Gras event held in many Cajun communities of south Louisiana on the Tuesday before Ash Wednesday.
 Courir de Mardi Gras is Cajun French for "Fat Tuesday Run".
 The rural Mardi Gras celebration is based on early begging rituals, similar to those still celebrated by mummers, wassailers and celebrants of Halloween.
 As Mardi Gras is the celebration of the final day before Lent, celebrants drink and eat heavily, and also dress in specialized costumes, ostensibly to protect their identities.
 Popular practices include wearing masks, capuchons, and costumes, overturning social conventions, dancing, drinking alcohol, begging, feasting, whipping, etc.
 Because of violent activities associated with the Ku Klux Klan, Louisiana has a state law prohibiting the wearing of hoods and masks in public.
 Mardi Gras is one of the few occasions when exceptions are allowed, as are Halloween celebrations and religious observances.
 Two HBO series (the crime drama "True Detective" and the post Hurricane Katrina themed "Treme") make reference to the tradition.
Nancy Drew is a fictional American character in a mystery fiction series created by publisher Edward Stratemeyer as the female counterpart to his Hardy Boys series.
 The character first appeared in 1930.
 The books are ghostwritten by a number of authors and published under the collective pseudonym Carolyn Keene.
 Over the decades, the character evolved in response to changes in US culture and tastes.
 The books were extensively revised and shortened, beginning in 1959, in part to lower printing costs with arguable success.
 In the revision process, the heroine's original character was changed to be less assertive and more feminine.
 In the 1980s, an older and more professional Nancy emerged in a new series, "The Nancy Drew Files", that included romantic subplots for the sleuth.
 The original "Nancy Drew Mystery Stories" series started in 1930, and ended in 2004.
 Launched that same year, the "Girl Detective" series features Nancy driving a hybrid electric vehicle and using a cell phone.
 In 2013, the "Girl Detective" series ended, and a new current series called "Nancy Drew Diaries" was launched.
 Illustrations of the character evolved over time to reflect contemporary styles.
 The character proves continuously popular worldwide: at least 80 million copies of the books have been sold, and the books have been translated into over 45 languages.
 Nancy Drew is featured in five films, two television shows, and a number of popular computer games; she also appears in a variety of merchandise sold around the world.
The holiday of Mardi Gras is celebrated in Southern Louisiana, including the city of New Orleans.
 Celebrations are concentrated for about two weeks before and through Shrove Tuesday, the day before Ash Wednesday (the start of lent in the Catholic tradition).
 Usually there is one major parade each day (weather permitting); many days have several large parades.
 The largest and most elaborate parades take place the last five days of the Mardi Gras season.
 In the final week, many events occur throughout New Orleans and surrounding communities, including parades and balls (some of them masquerade balls).
The Sydney Gay and Lesbian Mardi Gras, at one stage temporarily the Sydney Mardi Gras, or locally Mardi Gras, is an annual LGBT pride parade and festival in Sydney, Australia, attended by hundreds of thousands of people from around Australia and overseas.
 It is one of the largest such festivals in the world, and includes a variety of events such as the Sydney Mardi Gras Parade and Party, Bondi Beach Drag Races, Harbour Party, the academic discussion panel "Queer Thinking", Mardi Gras Film Festival, as well as Fair Day, which attracts 70,000 people to Victoria Park, Sydney.
Legend of the Crystal Skull is the 17th installment in the Nancy Drew point-and-click adventure game series by Her Interactive.
 It is available for play on Microsoft Windows platforms.
 It has an ESRB rating of E for moments of mild violence and peril.
 Players take on the first-person view of fictional amateur sleuth Nancy Drew and must solve the mystery through interrogation of suspects, solving puzzles, and discovering clues.
 There are two levels of gameplay, Junior and Senior detective modes, each offering a different difficulty level of puzzles and hints, however neither of these changes affect the actual plot of the game.
 The game is loosely based on a book entitled "The Mardi Gras Mystery" (1988).

Question: What state is the setting for the  Mardi Gras Mystery, the 81st book in the Nancy Drew mystery series?
Answer: Louisiana