Las Vegas is the county seat of San Miguel County. It is on I-25 after leaving the Sangre de Cristo mountains toward the eastern prairie. It was once two separate municipalities (one a city and the other a town), both were named Las Vegas—West Las Vegas ("Old Town") and East Las Vegas ("New Town") separated by the Gallinas River. The "Old Town" was established in 1835 by a group of Mexican settlers. The town was laid out in the traditional Spanish Colonial style whereby the town was planned according to the The Royal Ordinance of the Indes of 1573 or Colonization Laws of 1573, with specific instructions specifying that it have a central plaza surrounded by buildings which could serve as fortifications in case of attack. In 1846, Stephen W. Kearny delivered an address in the old Plaza of Las Vegas during the Mexican–American War claiming New Mexico for the United States. There is a monument in the plaza that states his address to the people from atop one of the buildings.

The Atchison, Topeka and Santa Fe Railway (the Burlington Northern & Santa Fe today) was constructed to the town in 1880 as it made its way west. To maintain control of development rights, it established a station and related development one mile east of the Plaza, creating a separate, rival "New Town."

Today there are various sights and activites in the area:

1. The Castaneda Hotel was built in 1898 and 1899 by the Atchison, Topeka and Santa Fe Railway, and was operated by the Fred Harvey Company until 1948. After being mostly vacant for many years, the hotel was restored and reopened in 2019. It is next to the town's railway station.

2. The Fourth of July Fiesta in the old Plaza is a fun event. There is music and dancing in the plaza all day with food and souvenir vendors all around the plaza.

3. The 2012 A&E TV series Longmire starring Robert Taylor and Katee Sackhoff and set in Wyoming was filmed in Las Vegas. Their sheriff's office and door from the plaza is still there.

4. The City of Las Vegas Museum & Rough Rider Memorial on Grand Avenue, dedicated in 1940, was first established by the decision of Theodore Roosevelt's Rough Riders regiment (the first Volunteer Cavalry Regiment of the Spanish–American War), who named Las Vegas its official reunion home. Their first reunion was held in Las Vegas, June 1899.

5. The Las Vegas National Wildlife Refuge is located just out of town off of NMHwy-104 toward Tucumcari. There is a nice circle drive in the refuge where you can see all different types of wildlife (both birds and other wild animals).

6. Montezuma Hot Springs is just out of town on NMHwy-65. Today there are three groupings of concrete soaking pools with sand and gravel bottoms of differing depths. At one time there was a hotel (The Adobe Hot Springs Hotel) there, but today there is very little evidence of any buildings there. There are several seeps nearby where the mud can be dug out to create primitive soaking pools.

7. Today the United World College occupies the old Montezuma Hotel (Montezuma Castle) located not far from the hot springs. In 1881, a new luxury hotel and the first building in the Southwest to have electric lighting and an elevator. It was constructed by the Fred Harvey Co. and the Atchison, Topeka and Santa Fe Railroad. Named the Montezuma Hotel, it opens to the public in 1882. It had a landscaped park with shops, a water fountain, and even a zoo is created behind the building.

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