It will be recalled that what became the Jefferson National Expansion Memorial and Gateway Arch began in late 1933 when Luther Ely Smith, a prominent Republican lawyer and civic activist, peered out of a train window at the shabby St. Louis riverfront and decided the city should do better.

One rigged election, one massive land clearance project and one world war later, Mr. Smith had a second idea: The as-yet-unbuilt memorial should have “a central feature, a shaft, a building, an arch, or something which would symbolize American culture and civilization.”

As his granddaughter, Christine Ely Smith, recalled in an oral history project for the National Park Service, Mr. Smith wanted something “transcending in spiritual and aesthetic values” that would attract visitors from other nations. Said Christine Smith: “He had a greater vision of the city than what it was. He felt that you needed to do something fairly dramatic to improve downtown, and attract people to downtown. He felt that the heart of the city was the river. That’s where the city had started, that’s where its roots were, that’s why it’s here in the first place.”

Sixty-five years later, John Claggett Danforth, another prominent Republican lawyer and civic leader, has been thinking similar thoughts. The former U.S. senator and United Nations ambassador and an heir to the Ralston Purina fortune is at the point Luther Ely Smith was in 1944: He has a vision of a riverfront and Arch grounds transformed into a massive magnet for visitors. He’s not sure what would do it. He just knows it has to be “something big.”

Mr. Danforth and his brother, William H. Danforth, the former chancellor of Washington University, are willing to spend $50 million from their family’s foundation and raise another $100 million for “something big.” They’ve enlisted the help of business and civic groups and political leaders from around the region.

Like Mr. Smith, Mr. Danforth proposes to hold an international architectural competition for a design for whatever big something is decided upon. It should be a big enough something that each of the 34,579 hotel rooms in the city of St. Louis, St. Louis County, St. Charles County, Madison County and St. Clair County would be filled 3.3 additional nights per year.

What would be big enough and cool enough to persuade more than 100,000 individuals and families to stay an extra night in St. Louis just to see it? Mr. Danforth is open to suggestions. Whatever it is could be operated by a private foundation in collaboration with the Park Service; Mr. Danforth would like to see it open by 2015, the 50th anniversary of the completion of the Arch.

St. Louis being St. Louis, lots of people scoffed at Luther Ely Smith’s vision, particularly in the teeth of the Great Depression and during World War II. Mr. Danforth, who has been focusing on riverfront development for more than eight years, also is finding the going tough.

He began with a simple, albeit expensive, concept of bridging the depressed lanes of Interstate 70 and Memorial Drive with a landscaped lid. That would have been combined with more visitor attractions (the idea of floating islands was floated) on the river’s edge. To look at the flooding Mississippi receding from the Arch’s steps today is to understand why that idea went nowhere.

Then, earlier this year, the Park Service agreed it might be time to amend its master plan for the Arch grounds. The Park Service is not quite as enamored of “something big” as Mr. Danforth, but it hasn’t ruled it out. The five alternatives currently being considered range from doing nothing to doing something big. A public introduction of some of these alternatives was held Wednesday evening in Forest Park. A second session is scheduled for Tuesday from 3 p.m. to 6:30 p.m. Tuesday at the Old Courthouse.

The Park Service will consider public comments when it decides on its new General Management Plan for its national memorial and grounds. At the very least, it should include “The Big Lid” bridging I-70 and Memorial Drive, connecting St. Louis to the river. There seems to be universal agreement on that. But the Park Service also should leave room for the possibility of “something big” to be named later.

Yes, that’s a vague concept, and final judgment ought to be reserved until there’s something specific to judge. But it’s worth keeping in mind that Luther Ely Smith’s dream in 1944 of “a shaft, a building, an arch, or something” was pretty vague, too. Eventually, that worked out spectacularly well.