Now that I've had some time, here's a list I've compiled from Jason Bryant's database.
3x All-Americans (7)
Dale Anderson (Waterloo) - Michigan State, 1966-67-68
Paul Martin (Algona) - Oklahoma State, 1975-77-78
Jason Kelber (Albion/West Marshall) - Nebraska, 1989-90-91
Tolly Thompson (Janesville) - Nebraska, 1995-96-97
Steven Blackford (WDM/Dowling) - Arizona State, 1999-2000-01
Mack Reiter (Gilbertville/Don Bosco) - Minnesota, 2005-06-08
Willie Miklus (Altoona/SE Polk) - Missouri, 2015-16-18
2x All-Americans (11)
Floyd Helgerson (Marshalltown) - Ohio State, 1928-30
Dale Hanson (Cresco) - Minnesota, 1939-40
L. Wayne Smith (Fort Dodge) - Michigan 1946; Navy 1950
Garth Lappin (Cresco) - Minnesota, 1947-49
Norvard Nalan (Mason City) - Michigan, 1953-54
Mike Natvig (Decorah) - Army, 1962-63
Mike Nissen (Mason City) - Nebraska, 1962-63
Gerald Malecek (Belle Plaine) - Michigan State, 1970-72
Al Freeman (Griswold) - Nebraska, 1981-83
Jeff Theiler (DSM/Dowling) - Arizona State, 1994-95
James Nicholson (DSM/Roosevelt) - Old Dominion, 2008-11
1x All-Americans (27)
Ralph Lupton (Marshalltown) - Northwestern, 1928
Blair Thomas (Cresco) - Michigan, 1928
Earl Thomas (Cresco) - Michigan, 1936
Harold Nichols (Cresco) - Michigan, 1940
John Roberts (West Des Moines) - Wisconsin, 1941
Frank Hirt (Mason City) - Michigan, 1956
Bill Wright (Waterloo) - Minnesota, 1959
Dave Hansen (Britt) - Wyoming, 1960
Harold Thompson (Osage) - Nebraska, 1962
Mike Harman (New Hampton) - Navy, 1963
Larry Lloyd (Britt) - Minnesota, 1964
Bob Steenlage (Britt) - Army, 1966
Don Miller (Eagle Grove) - Wyoming, 1967
Al Borkowski (Audubon) - Northwest Missouri, 1968
Wydell Boyd (Davenport/Central) - Northwestern, 1970
Joe Corso (West Des Moines) - Purdue, 1975
Phil Callahan (Clinton) - Illinois, 1986
Jeff Castro (Bettendorf) - Montana, 1987
Dan Costigan (Lawler/Turkey Valley) - Army, 1987
Kirk Azinger (DeWitt) - Illinois, 1988
Joe Malecek (Osage) - Nebraska, 1990
Pat Waters (Iowa City High) - Cornell, 1990
Brad Canoyer (Griswold) - Nebraska, 1995
Terry Parham (Pacific Junction/Glenwood) - Air Force, 2002
Brandon Mason (Shenandoah/Lewis Central) - Oklahoma State, 2007
Andrew Long (Creston) - Penn State, 2011
Josh Ihnen (Sheldon) - Nebraska, 2012