The tower on San Francisco’s landmark Ferry Building is about to get a new look to make it appear just the way it did a century ago.

The numerals 1915 will be installed on the tower in figures 11 feet, 6 inches high. The four numbers together will be 27 feet long. The 240-foot tower will be illuminated at night in white lights, exactly as it appeared during the Panama-Pacific International Exposition.

The lights and the numbers were originally installed on the Ferry tower to celebrate the 1915 exposition, and they are being reinstalled to mark the 100th anniversary of the fair, which transformed more than 600 acres in what is now the Marina into a fairyland of palaces and amusement rides. It was such a hit, it is still a fond civic memory.

The project to light the Ferry Building was the brainchild of Donna Ewald Huggins, a leading historian of the fair. She has written a book on the exposition and has a huge collection of artifacts and fair ephemera.

The idea came to her in the middle of the night not long ago, “like a vision,” she said last week.

Back a century ago, the Ferry Building was the symbol of San Francisco, by far the busiest passenger terminal in the West. In the days before the bridges, almost everyone who arrived in San Francisco came through that building at the foot of Market Street.

“It was the first thing everybody saw when they came to San Francisco,” Huggins said. “It would be difficult to underestimate the importance of the Ferry Building in 1915.”

That’s why the Ferry Building was transformed to advertise the fair, which was the biggest thing to hit San Francisco since the 1906 earthquake.

Help from philanthropist

Besides the numbers and lights on the tower, a 550-foot-long neon sign was put up on the bay side of the building. “California Welcomes the World,” it said. On the other side of the tower, another neon sign said: “Panama-Pacific Exposition.”

Reproducing the big signs seemed too difficult, but Huggins thought the “1915” sign and the lights were doable.

She contacted Jim Phelan, a steeplejack who loves tall buildings and history in equal measure. Phelan agreed to fabricate the big numbers and install them on the Ferry Building tower. But city authorization was needed. Huggins then talked to Mayor Ed Lee, who was enthusiastic, she said. So was the Port of San Francisco, which owns the Ferry Building, and Equity Office, which manages the building.

The total cost would be about $80,000. The city liked the idea but didn’t want to put up public money. So Huggins hit the phones and by the middle of January had about half the amount raised. But the fair opened on Feb. 20, 1915, and the clock was ticking.

Huggins called philanthropist Tad Taube, who had made a sizable donation to the restoration of the Palace of Fine Arts, the last surviving building from the 1915 fair. “He said, 'I’ll do it,’” Huggins recalled. “He put up $35,000 at the last minute.”

Phelan signed on, and Metropolitan Electric will do the lights, which will all be LED and very low power, only 0.7 watts per bulb.

So the deal is on, and work will start in a few days. Huggins, Phelan and port officials went up on the tower last week to scope out the project. The big numbers will be installed about three-fourths of the way up the tower, above the clock.

There will be two sets of numbers, one facing San Francisco and the other facing the bay. Strips of light will be strung on the edges of the tower, illuminating all the tower’s lines. The result will be visible from both San Francisco and the East Bay.

Display to last 9 months

The lights will go on just after 6 p.m. on March 3,which is the closest Huggins could get to the opening date of the fair. There will be an appropriate ceremony in front of the Ferry Building.

The display will last nine months. The lights will go out on Dec. 4, the day the fair closed a century ago, and the Ferry Building will be restored to its 21st century appearance.

“This to me tells tells the whole story of the spirit of 1915,” Huggins said.

Carl Nolte is a San Francisco Chronicle staff writer. E-mail: cnolte@sfchronicle.com

Twitter: @carlnoltesf

Learn more

For more information on the anniversary, visit www.ppie100.org.