Pope Francis delivers his message on the occasion of an audience with participants of Rome's diocese convention in St. Peter's Square, at the Vatican, Sunday, June 14, 2015. (Gregorio Borgia/AP)

As Pope Francis prepares for his historic visit to the United States next month, Washington is bracing for the arrival of one of the most popular popes in memory with a familiar mix of joyful anticipation and dread.

The rush is on for tickets to view the pope’s address to a joint meeting of Congress, something no pope has done, or to attend the pope’s outdoor Mass at the Shrine of the National Basilica of the Immaculate Conception. Environmentalists have secured a permit for 200,000 for a rally on the Mall to highlight the pontiff’s stance on protecting the planet. Souvenirs and life-size pop-ups of the pope are cropping up, and the Washington Archdiocese has even unveiled a social media hashtag — #PopeinDC — to help Francis fans keep up with the Holy Father’s travels.

City, state and federal officials said they are planning for an event on a scale of presidential inaugurations.

“We anticipate very, very large crowds . . . much earlier than prior to the pope coming up the Capitol, lining all of the streets,” U.S. Capitol Police Chief Kim Dine told a Senate panel earlier this year. “That is a huge event, and something frankly that goes above and beyond our budget.”

Behind the scenes, Dine’s agency and other top law enforcement officials have been laying plans for a vast, multilayered security cordon to ensure the safety of the pope and the hundreds of thousands of people who are expected to see him. Transit officials are taking steps to move extra crowds and manage the gridlock that comes with high-profile motorcades.

Dave Cahoon begins work on the altar that will be used by Pope Francis during his visit to Washington, seen here earlier this month in Poolesville, Md. (Katherine Frey/The Washington Post)

The pope is expected to arrive Sept. 22 at Joint Base Andrews in Prince George’s County to begin his six-day trip — the first time the 78-year-old Argentine has visited the United States. The following day, he will pay a visit to the White House, meet with U.S. bishops at the Cathedral of St. Matthew the Apostle and celebrate Mass from the east portico of the basilica. During the Mass, he will canonize Junípero Serra, an 18th-century Franciscan friar who founded missions in California. The pope will address Congress on Sept. 24. That night he will depart for stops in New York and Philadelphia, which is hosting the World Meeting of Families.

Pope Francis’s popularity has soared since he began his papacy a little more than two years ago, especially among non-Catholics and disaffected Catholics who prefer his emphasis on helping the poor, fighting for social justice and protecting the environment, rather than on hot-button sexual issues on which Catholics disagree. (Conservatives in the United States at times struggle with his critique of capitalism and wish he would make more references to those sexual teachings.) A March 2015 report by the Pew Research Center found that Pope Francis enjoyed a 90 percent favorability rating among U.S. Catholics and a 70 percent favorability rating among all Americans.

“He is a rock star. And in that regard, I know we’re going to have a regional draw of people coming into the city,” said Elliott L. Ferguson II, president and chief executive of Destination DC, a convention and tourism promoter. But Ferguson said turnout could be smaller than for Pope Benedict XVI’s trip to Washington more than seven years ago, because many people will have just returned to school or work after the summer. Unlike during Benedict’s 2008 visit, which helped drive hotel occupancy rates above 95 percent, no major conventions are scheduled next month.

For Washington’s Catholics — who number more than a million — the papal visit will be the third in nearly 25 years. Of nine previous visits to the United States, two have included stops in Washington, including those of Francis’s two predecessors: Pope John Paul II became the first pope to visit the White House in 1979, while Benedict celebrated Mass in front of 47,000 people at Nationals Park soon after its opening.

There are now about 620,000 parishioners in the Archdiocese of Washington, which includes parts of Maryland, and 450,000 in the Arlington Diocese, which includes northeastern Virginia. The District’s Catholic population also includes many prominent figures, including members of Congress, Supreme Court justices and activists who lobby on topics including housing and abortion.

The Catholic Church has deep historical roots in the area. When settlers landed on Maryland’s St. Clement’s Island in 1634, the Rev. Andrew White, a Jesuit priest, said the first Catholic Mass in what would become the United States.

“I think everybody’s excited about the visit and just wanting to take part in what’s going on,” said Ursula Higgins, who chairs the District’s Neighborhood Advisory Committee in Brookland, an area known as “Little Rome” because of the many Catholic institutions there.

While Pope Francis will make multiple stops in Washington, including a lunchtime visit with Catholic Charities clients, one of the biggest events here — and perhaps the best chance Catholics have of seeing him — will be the Mass at the basilica. A rally on the Mall, at which the pope may appear, has given people hope of another chance at seeing the pontiff in person.

Cardinal Donald Wuerl, archbishop of Washington, said in announcing the pope’s visit that the 25,000 seats at the basilica would be distributed through parishes, under any system the priests might like, as was done in 2008 for Benedict’s Mass at Nationals Park.

But they are intended for people active in parish and Catholic life, particularly Spanish-speaking immigrants eager to see the first Latino pope, Wuerl said.

Monsignor Ronald Jameson, rector of St. Matthew’s Cathedral, said he is doling out tickets the same way he did for Benedict’s visit, by asking people to send him a letter answering two questions: “Why on earth would you want to go to a papal Mass?” And, “What are you doing in your parish or Catholic life that would connect you with what Pope Francis is talking about?”

Replies have come from a man who said Francis had inspired him to begin the path to priesthood, a Jewish man who said he was volunteering more with his Catholic wife, and a Latino woman who called the pope her “hero.”

On Capitol Hill, the method of choice for giving out tickets to the pope’s address appeared to be trusting to chance — or perhaps divine intervention — in the form of a lottery. The most-coveted tickets are for seats in the gallery: Each member was given only one. House members also were allotted one ticket each for a member of the public to view a simulcast in the Cannon Caucus Room and an additional 50 tickets to view the address on Jumbotrons on the Capitol’s West Lawn. Senators received 100 pairs of outside tickets.

Rep. John K. Delaney (D-Md.), an observant Catholic, said he is thrilled about the visit. As a boy, Delaney often attended Mass not only on Sunday but every Tuesday night with his mother.

“It’s always been an important part of who I am,” Delaney said, though acknowledging that his views on same-sex marriage, birth control and abortion diverge from church teachings. He welcomed Francis’s renewed emphasis on social justice and helping the poor.

“Not only is he the most popular person in the world right now, but I think he has helped refocus the church that I love so much on the things that have always made me most proud to be a Catholic,” Delaney said. His gallery ticket is going to his wife, who converted to Catholicism.

Catholic advocates are also eagerly awaiting Francis’s arrival in a quintessentially Washington way: crafting legislation tied to the pope’s visit.

Kristen Day, executive director of Democrats for Life, said abortion opponents will push for a Senate vote on a measure to ban abortion after 20 weeks of gestation. The group is also highlighting other measures that fit with Francis’s priorities, including a bill sponsored by Sen. Kirsten Gillibrand (D-N.Y.) that would create paid family leave.

“The pope’s visit will push people out of their comfort zone,” Day said.

Top law enforcement officials, including D.C. police, Vatican officials and the Secret Service, were reluctant to discuss their preparations, either because they were still making plans or because they did not want to reveal details that could compromise the pope’s security.

In interviews and testimony this year before Congress, however, several law enforcement officials made it clear that they anticipate an event of monumental proportions.

Scott White, an associate professor of national security at Drexel University in Philadelphia, said the task of those involved in protecting the pope is enormous.

“The United States will always remain a target for adversaries,” White said. “And the pope himself is a target. He represents a billion people around the planet, and he is an internationally protected person. This is what keeps intelligence officers up at night.”

Metro probably will boost service for the visit, detour buses and close some Metro entrances near papal events, spokesman Dan Stessel said. (Changes in service will also depend on whether the D.C. and federal governments offer workers liberal leave during days the pope will be in the city.)

Amtrak will likely add more trains to accommodate people traveling for the events in Washington, Philadelphia and New York, spokeswoman Kimberly Woods said. Although Washington officials have not released a traffic diagram and management plans for the pope’s visit as Philadelphia has, they said commuters should expect significant disruptions from road closures and restricted zones.

“It won’t be a typical motorcade, and it won’t be typical traffic jams,” said John B. Townsend II of AAA Mid-Atlantic. “This is beyond rock-star status.”

An earlier version of this story incorrectly stated that Pope Francis is 79. He is 78.

Peter Hermann and Luz Lazo contributed to this report.