Question: How many visitors, international and domestic, visit the place where three of the state's four largest incorporated cities are located?

Context paragraphs:
List of largest California cities by land area: This is a list of the 25 largest incorporated cities in the State of California ranked by land area.

Las Vegas Valley: The Las Vegas Valley is a major metropolitan area located in the southern part of the U.S. state of Nevada.  The largest urban agglomeration in the state, it is the heart of the Las Vegas–Paradise-Henderson, NV MSA.  The Valley is largely defined by the Las Vegas Valley landform, a 600 sqmi basin area surrounded by mountains to the north, south, east and west of the metropolitan area.  The Valley is home to the three largest incorporated cities in Nevada: Las Vegas, Henderson and North Las Vegas.  Five unincorporated towns governed by the Clark County government are part of the Las Vegas Township and constitute the largest community in the state of Nevada.

List of cities in Alaska: Alaska is a state of the United States situated in the northwest extremity of the North American continent.  According to the 2010 United States Census, Alaska is the 4th least populous state with 710,231 inhabitants but is the largest by land area spanning 570640.95 sqmi .  s of 2014 , Alaska has 148 incorporated cities: four unified home rule municipalities, which are considered both boroughs and cities, ten home rule cities, nineteen first class cities and 115 second class cities.  As reflected in the 2010 Census, Alaska's incorporated cities cover only % of the territory's land mass but are home to % of its population.  The majority of the incorporated land mass consists of the four unified municipalities, each over 1700 sqmi in size.  Only two other cities have an incorporated area exceeding 100 sqmi : Unalaska, which includes the fishing port of Dutch Harbor, and Valdez, which includes the terminus of the Trans-Alaska Pipeline System.

Nevada: Nevada (Spanish for "snowy"; see pronunciations) is a state in the Western, Mountain West, and Southwestern regions of the United States of America.  Nevada is the 7th most extensive, the 34th most populous, but the 9th least densely populated of the 50 United States.  Nearly three-quarters of Nevada's people live in Clark County, which contains the Las Vegas–Paradise metropolitan area where three of the state's four largest incorporated cities are located.  Nevada's capital is Carson City.  Nevada is officially known as the "Silver State" because of the importance of silver to its history and economy.  It is also known as the "Battle Born State", because it achieved statehood during the Civil War (the words "Battle Born" also appear on the state flag); as the "Sagebrush State", for the native plant of the same name; and as the "Sage-hen State".  Nevada borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast and Utah to the east.

Blackford County, Indiana: Blackford County is located in the east central portion of the U.S. state of Indiana.  The county is named for Judge Isaac Blackford, who was the first speaker of the Indiana General Assembly and a long-time chief justice of the Indiana Supreme Court.  Created in 1838, Blackford County is divided into four townships, and its county seat is Hartford City.  Two incorporated cities and one incorporated town are located within the county.  The county is also the site of numerous unincorporated communities and ghost towns. Occupying only 165.58 sqmi , Blackford County is the fourth smallest county in Indiana.  As of the 2010 census, the county's population is 12,766 people in 5,236 households.  Based on population, the county is the 8th smallest county of the 92 in Indiana.  Although no interstate highways are located in Blackford County, three Indiana state roads cross the county, and an additional state road is located along the county's southeast border.  The county has two railroad lines.  A north–south route crosses the county, and intersects with a second railroad line that connects Hartford City with communities to the west.

List of largest Iowa cities by population: This is a list of the 30 largest incorporated cities in the State of Iowa ranked by population, based on the reported results of the 2016 United States Census population estimates.

Las Vegas–Paradise, NV MSA: The Las Vegas–Paradise, NV MSA, also known as the Las Vegas–Henderson–Paradise, NV Metropolitan Statistical Area (2013), is in the southern part of the U.S. state of Nevada, coextensive since 2003 with Clark County, Nevada.  A central part of the metropolitan area is the Las Vegas Valley, a 600 sqmi basin that includes the metropolitan area's largest city, Las Vegas as well as the other primary city, Paradise, Nevada.  The area contains the largest concentration of people in the state.  Cities in the metropolitan area include Las Vegas, Henderson, North Las Vegas, and Boulder City.  The metropolitan area is one of the top tourist destinations in the world, drawing over 40 million international and domestic visitors in 2013 with a GMP of US$103.3 billion.

Mudu: Mudu (; Suzhou Wu: Moh doh, ] ) is a town in Wuzhong District, Suzhou, Jiangsu province, China.  It takes about 1.5 hours to drive from the downtown in Suzhou to Mudu.  Mudu is a small town which is famous for its history.  During the Qing dynasty, the Qianlong Emperor visited Mudu six times when he traveled around the country.  Nowadays, many teleplay groups also come to Mudu frequently to film television series.  Due to this, many outlanders came to Mudu to make their business by renting out costumes and taking photos for visitors.  There is a famous street in Suzhou named Shantang Street, Mudu also has one.  It is shorter than the one in Suzhou downtown, but if you go straight along the street, one can approach to the Linyan Mountain, many visitors will first visit this mountain when they visited Mudu.

Rockville, Maryland: Rockville is a U.S. city located in the central region of Montgomery County, Maryland.  It is the county seat and is a major incorporated city of Montgomery County and forms part of the Baltimore–Washington metropolitan area.  The 2010 census tabulated Rockville's population at 61,209, making it the third largest incorporated city in Maryland, behind Baltimore and Frederick.  Rockville is the largest incorporated city in Montgomery County, Maryland, although the nearby census-designated place of Germantown is more populous.

Angling in Yellowstone National Park: Angling in Yellowstone National Park is a major reason many visitors come to the park each year and since it was created in 1872, the park has drawn anglers from around the world to fish its waters.  In 2006, over 50,000 park fishing permits were issued to visitors.  The park contains hundreds of miles of accessible, high-quality trout rivers containing wild trout populations—over 200 creeks, streams and rivers are fishable.  There are 45 fishable lakes and several large lakes are easily accessible to visitors.  Additionally, the park's remote sections provide anglers ample opportunity to visit rivers, streams, creeks and lakes that receive little angling pressure.  With the exception of one specially designated drainage, all the park's waters are restricted to artificial lures and fly fishing.  The Madison, Firehole and a section of the Gibbon rivers are restricted to fly fishing only.

Supporting paragraphs: Nevada Las Vegas–Paradise, NV MSA
Answer: 40 million