There are 75 unpublished items by Mary Ellen Solt at Indiana University's Lily Library. The earliest of these date from 1960. Present are letters from Robert Creeley, Denise Levertov, George Oppen, John Thirwall, and Louis Zukofsky. Also present is a notebook prepared and titled by Solt "Index to Robert Creeley Ms Material--Lilly Library"; two Christmas cards from Florence (Mrs. William Carlos Williams); a holiday card and two color transparencies from Paul Williams relating to his father, William Carlos Williams; and a file of eighteen photographs and negatives of William Carlos Williams and family members.
John ("Jack") Thirwall was supposed to be an official biographer of Williams. His book never came out, and I've for years tried to find out what happened to Thirwall and/or his project. No luck so far. I'm guessing that the Thirwall materials here are letters from him to Solt asking about WCW.
Kenny Goldsmith's UBUweb has her entire Flowers in Concrete (1966) here. UBU also has an essay by Solt on the origins of concrete poetry in Brazil.

Is '60 the moment when the end of the end of the Old Left had been reached and the New Left began to emerge? Is it the final ascendancy, in certain scenes at least, of poetic postmodernity? Surely the publication of Donald Allen's The New American Poetry that year suggests this, but then again--once again--we look back on "New" here and see continuity. The rhetoric of the Kennedy-Nixon contest made much less of a dent than everyone (at the time as well as since) claimed, so one wonders why were such great claims made?
Had we come to expect "1960" to be truly ubiquitously modern in a way that the 1950s really were not--not quite? And what specifically does "modern" mean in the Kennedyesque talk then and now about the torch being passed to a new generation, etc.? The First Lady really meant "modernist" when Camelotians said "modern." What about the others across the new young cultural leadership? I've been surprised by how frequently the
"Beat movement" was covered in 1960 in the mainstream press. I was expecting a fair measure but I've found tonnage. 1960 was the year when the figure of the beat was beginning to find acceptance, although still 80% of these stories are mocking, rebels-without-cause condescension. For anyone whose analysis made an impact nationally, do these antipolitical adolescents count as part of the "new young cultural leadership"? No, but rather than the two being opposites, they fall along a Continuum of the New American. Now that's a change for '60.