Muhammad Ali's legendary presence made him a natural ambassador for the center bearing his name. His family and friends hope his death won't stop fans from opening their checkbooks to support his legacy in the city where his boxing career started.

Ali's death in June at age 74 after a long battle with Parkinson's disease left the Muhammad Ali Center without its co-founder and guiding force.

"It really made us stop and reflect even more about what's next. What happens after the champ is gone?" Louisville Mayor Greg Fischer said.

The center showcases his fights inside the ring and outside of it — against war and segregation. Ali Center officials have an ambitious fundraising campaign and hope to further promote the ideals championed by Ali: peace, social justice and personal growth.

Meanwhile, a renovation of exhibit space, planned before his death, opens to the public in September with new artifacts.

Ali's wife, Lonnie, said the center's efforts embody her husband's humanitarian goals.

"Muhammad was very proud of the Muhammad Ali Center and his genuine desire was that it last for generations to come as an example of how people should live their life," said Lonnie Ali, who co-founded the center.

The burst of activity comes as the center, a striking structure along the Ohio River that opened in 2005, tries to build on the outpouring of interest in the three-time heavyweight boxing champion.

"So many people ... had absolutely no idea that Muhammad Ali was from Louisville," said Ali Center President and CEO Donald Lassere.

Fans flocked to Ali's hometown after his death. Tens of thousands lined Louisville streets for his funeral procession before a star-studded memorial service.

In the first week after he died, the Ali Center's attendance surged to 20,000 people. In 2015, visitors totaled about 100,000. The upswing continued in July and August. Gift shop sales have skyrocketed.

The initial phase of the fundraising campaign, focused on Louisville, has a goal of $10 million. About $1 million has been raised so far. The campaign will expand globally, with an ultimate goal of $100 million.

"Fundraising needs to occur right now while all that's kind of fresh in people's mind," said Ina Brown Bond, a longtime Ali Center supporter.

Donations account for about 70 percent of the Ali Center's income, officials said. The rest comes from admissions, memberships, retail sales and private events. The center's annual budget is about $4.5 million.

Lassere acknowledged that fundraising will likely become more difficult as years pass.

An annual event bestowing Ali humanitarian awards is an important fundraising occasion. This year's awards ceremony will be Sept. 17, and recipients include Cindy Hensley McCain, wife of Arizona Sen. John McCain, and Academy Award-winning actor Louis Gossett Jr.

Still, officials acknowledge that Ali's death leaves a void.

"How do you overcome (the loss) of the greatest of all time?" Lassere said. "You have ... to have the confidence to move forward."

Supporters say the center will stay relevant by promoting Ali's humanitarian principles while delving into discussions about bridging racial and religious divides.

"The Ali Center should be one of the premiere gathering places in the world for these types of conversations," said Fischer, the mayor. "Because what the Muhammad Ali Center has that nobody else has is Muhammad Ali.

"There's only one of him."