The cover image for the U.S. edition of “The Americans,” Robert Frank’s epochal book, spoke volumes about the state of the nation in the mid-1950s. The tightly-cropped photo shows passengers in the windows of a New Orleans trolley assuming their place in the social order of the Jim Crow South — progressing from a black woman in the rear to white children and adults up front (slide 4).

The contact sheet that contained the image showed that Mr. Frank had photographed the city from multiple perspectives, but he ultimately selected the frame that most dramatically and symbolically captured New Orleans’ racial hierarchy. Learning this photo’s backstory would be impossible without the ability to view Mr. Frank’s contact sheet. Now, such important archival material, typically reserved for scholars and curators, is just a click away. Launched by the National Gallery of Art in time for photographer’s 90th birthday in November, the Robert Frank Collection Guide is an extraordinary resource for the general public and researchers alike.

The online guide is a first for a photographer in the National Gallery collection. Mr. Frank’s work was selected because it constitutes the museum’s largest and most complex holding by a single photographer. Spanning his career from 1937 to 2005, the collection includes more than 8,000 items, including vintage and later prints, work prints, negatives, contact sheets, technical material, recordings, and ephemera. Nearly all of these artifacts were acquired from Mr. Frank in stages over the past twenty-five years.

The guide’s production was overseen by Sarah Greenough, senior curator and head of the department of photography at the National Gallery, with a web team that included Sarah Gordon, who wrote most of site’s content, and John Gordy, who designed it.

“Because of the size, scope, and complexity of our Frank Collection,” Ms. Greenough said, “I realized many years ago that we needed such a finding guide. Yet it was while I was working on our exhibition and publication ‘Looking In: Robert Frank’s The Americans’ that I fully understood how hard it could be determine all the different iterations — from contact sheets, to work prints, to finished exhibition prints — that we might have of any one image. From then on, I knew that it was a project we had to undertake.”

Ms. Greenough would appear to be the perfect steward of Mr. Frank’s archive. She discovered “The Americans” in college and remembered being particularly fascinated by one photograph, “Canal Street, New Orleans,” especially by the expression on the face of a young girl being carried by her father.

“The girl seemed to express all the confused, uncertain feelings I had as a young person about American society and culture,” Ms. Greenough said. “That picture, along with others in ‘The Americans,’ made me realize for the first time how profoundly moving and important photography could be when done by someone like Robert Frank.”

Ms. Greenough’s scholarship on Mr. Frank reached its apex in “Looking In,” the traveling exhibition she organized for the National Gallery in 2009. The show was uncommonly rigorous, revealing myriad details about the conception and creation of “The Americans.” It was also visually bracing. Vintage photographs of differing sizes were arranged in groups that followed the sequencing of the book, producing dramatic shifts in scale, emphasis, and visual points of view.

Contact sheets and work prints provided greater context for the exhibition, and contributed to a viewing experience that was wholly different from reading “The Americans,” yet offering an array of new facts and observations about it. One wall, for example, was covered with tattered work prints, yielding insights into Mr. Frank’s process of selecting and rejecting images for the final work.

Like the exhibition, the catalog for “Looking in” was distinguished by its rigorous scholarship. Its expanded, special edition, which included the full contents of “The Americans,” as well as scholarly essays, facsimiles of contact sheets, photographer notes and correspondences, and other archival materials, functioned much like a massive and comprehensive finding guide, though limited to only one of Mr. Frank’s projects.

The online collection guide captures much of this dynamism. While it includes only a modest portion of the museum’s holdings at this point, it provides access to a broad range of images and information. And like “Looking In,” it helps us to better understand the work of one of the most important and influential photographers of the past seventy-five years. It also serves as a template for the National Gallery’s next online guide, documenting its large collection of Alfred Stieglitz photographs.

Ms. Greenough anticipates that the guide will serve a number of audiences and functions. “We hope that the general public will find it an informative overview of Frank’s work and his seminal contributions to American art and culture,” she said. “We also expect that scholars and photographers who want to study Frank’s work in-depth will discover vast amounts of information about him and his art that is not available anyplace else.”

Maurice Berger is a research professor and the chief curator at the Center for Art Design and Visual Culture at the University of Maryland, Baltimore County, and a consulting curator at the Jewish Museum in New York.

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