According to Crain’s New York, the Statue of Liberty and Ellis Island attracted 4.2 million visitors last year—the islands’ third biggest year in visitation after 1999 and 2000. The latter was the peak year, netting 4.4 million visitors.

In 2014 the numbers skyrocketed to 55 million visitors, an increase from 54.3 million in 2013, according to the city’s tourism bureau, NYC & Company. Tourism has steadily improved over the past 15 years with the exception of 2001 and 2009.

After the attacks on September 11, the number of visitors to the islands dropped because the National Park Service was forced to implement airport-style security measures before passengers could board boats, increasing the wait time to two hours and discouraging tourists from visiting.

A major factor in 2014′s strong numbers is the improved security clearance process at Battery Park, according to Statue Cruises, which has the exclusive contract to bring visitors to Liberty and Ellis islands.

“We have brought the wait times down from two hours to 20 minutes on a busy day,” said Michael Burke, chief operating officer of Statue Cruises.

The National Park Service added three security lanes for a total of seven, along with extra magnetometers and X-ray machines in the summer of 2013 to help boost attendance at the attractions, which had suffered after Hurricane Sandy. The islands experienced extensive damage and were closed for more than half a year after the storm in October 2012.

Last year, the service also extended the islands’ hours during the summer, allowing visitors to stay as late as 7:15 p.m., which resulted in an additional 60,000 visitors. The extended hours encouraged tourists to squeeze in a visit to the islands during their stay in the city.

“A normal good year for us would have been 3.8 or 3.9 million visitors,” Mr. Burke said. “This was an extraordinary year.”