The press release:

Pope Francis has created the Archdiocese of Las Vegas and named the Most Reverend George Leo Thomas, Ph.D., as the first Metropolitan Archbishop of Las Vegas. 

“28 years ago, Las Vegas became a Diocese, and now on May 30 an Archdiocese. This speaks to the tremendous growth and vibrancy of the local faith and the commitment of the women and men that serve in leadership including our priests. This really is a remarkable legacy and moment in Las Vegas, and for the Catholic Church as a whole,” commented Archbishop Thomas. “With our Diocese being elevated to an Archdiocese, Pope Francis has discerned the need for a new Ecclesiastical Province in the Western United States. I am deeply honored and humbled by this significant recognition by the Pope.”

“Being created an Archdiocese by Pope Francis at this moment in Las Vegas history certainly reflects the Holy Father’s confidence in the spiritual leadership of this Church under Archbishop Thomas these past five years,” remarked Bishop Gregory W. Gordon, Auxiliary Bishop of Las Vegas.

Read more. 

The archdiocese offers a helpful Q&A on its website: 

An ecclesiastical province is a territory consisting of an Archdiocese (known as the “metropolitan See”) and includes several Dioceses (known as “suffragan Sees”). The metropolitan archbishop is the head of his Archdiocese, and while he has no direct power of governance over the suffragan Dioceses in his province, through canon law (Church law), he supports them in matters of faith and discipline and provides fraternal pastoral care to his brother Bishops. In this newly created province, the Archdiocese of Las Vegas is the metropolitan see, and the Diocese of Reno and the Diocese of Salt Lake City are the suffragan Sees. A Metropolitan Archdiocese is a higher-level ecclesiastical jurisdiction within the Catholic Church. It serves as the central authority over a group of Dioceses in a specific region, known as a province.

A Metropolitan Archdiocese is established by the Holy See (the Vatican) based on certain criteria, such as the size, population, importance of the region, and other factors. The Diocese of Las Vegas was elevated to the Archdiocese of Las Vegas after a lengthy consultation process.