Slightly modified present-day scenario from
here. This timeline isn't triggered by the Oklahoma schools staying in the SWC, but that is an early development in the timeline.
P5 Conferences
ACC (9-game conference schedule, 2 protected crossovers per team)
Atlantic: Clemson (UGA/GT), South Carolina (UGA/GT), Miami-FL (UF/FSU), Virginia Tech (UF/FSU), NC State (Duke/UNC), Virginia (Duke/UNC)
Coastal: Georgia (Clemson/SC), Georgia Tech (Clemson/SC), Florida (Miami/VT), Florida State (Miami/VT), Duke (NCSU/UVA), North Carolina (NCSU/UVA)
Big 12 (8-game conference schedule, no protected crossovers)
East: Illinois, Indiana, Minnesota, Northwestern, Purdue, Wisconsin
West: Iowa, Iowa State, Kansas, Kansas State, Missouri, Nebraska
Big East (9-game conference schedule, 1 protected crossover per team)
North: Boston College (UMD), Michigan (OSU), Michigan State (WVU), Notre Dame (Pitt), Rutgers (Temple), Syracuse (PSU)
South: Maryland (BC), Ohio State (UMich), West Virginia (MSU), Pitt (ND), Temple (Rutgers), Penn State (Syracuse)
Pac-12 (9-game conference schedule, 2 protected crossovers per team)
Pacific: Arizona (ASU/Utah), Colorado (ASU/Utah), California (Stanford/USC), UCLA (Stanford/USC), Oregon (OSU/WSU), Washington (OSU/WSU)
Western: Arizona State (UA/CU), Utah (UA/CU), Stanford (Cal/UCLA), USC (Cal/UCLA), Oregon State (UO/UW), Washington State (UO/UW)
SEC (8-game conference schedule, no protected crossovers)
East: Alabama, Auburn, Kentucky, Mississippi State, Ole Miss, Tennessee
West: Arkansas, LSU, Oklahoma, Oklahoma State, Texas, Texas A&M
Other I-A Conferences
Metro (8-game conference schedule, no protected crossovers)
North: Army, Buffalo, Cincinnati, Louisville, Marshall, Navy
South: Appalachian State, Central Florida, East Carolina, Georgia Southern, Old Dominion, South Florida
SWC (8-game conference schedule, no protected crossovers)
East: Arkansas State, Louisiana Tech, Louisiana-Lafayette, Memphis, Southern Miss, UAB
West: Baylor, Houston, TCU, Texas Tech, Tulsa, Wichita State
WAC (8-game conference schedule, no protected crossovers)
Mountain: Air Force, BYU, Colorado State, New Mexico, UTEP, Wyoming
Pacific: Boise State, Fresno State, Hawaii, Nevada, San Diego State, UNLV
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Major differences from our timeline
1910s
-- Eastern Athletic Conference (EAC) forms with Michigan Agricultural (later Michigan State), Notre Dame, Ohio State, Pittsburgh, Penn State, and Syracuse
1920s
-- SoCon forms without Maryland and West Virginia, which join EAC
-- Oklahoma and Oklahoma A&M (later Oklahoma State) do not leave SWC for MVIAA; breakup of MVIAA postponed
1930s
-- Florida, Georgia, and Georgia Tech remain with SoCon rather than joining SEC
1940s
-- Michigan from Western Conference to EAC; EAC renamed Big East
-- Iowa State, Kansas, Kansas State, Missouri, and Nebraska from MVIAA to Western Conference (renamed Big 12)
-- Colorado stays in the MSC
1950s
-- ACC forms with Florida, Georgia, Georgia Tech, and Virginia Tech but not Maryland
1970s
-- South Carolina sticks with ACC
-- Colorado joins the Pac-8/11 along with Arizona and Arizona State
1980s
-- Several schools drop football and leave D1 for D3 Magnolia League: Rice (SWC), SMU (SWC), Tulane (I-A Ind; NFB in Metro), Vanderbilt (SEC), and Wake Forest (ACC)
-- Arkansas, Oklahoma, Oklahoma State, Texas, and Texas A&M from SWC to SEC
-- SWC adds Memphis, Southern Miss, Tulsa, and Wichita State (which does not drop FB); SWC no longer considered "power" conference
1990s
-- ACC adds Florida State and Miami
-- Big East adds Boston College, Rutgers, and Temple
-- Metro Conference adds football: Army, Central Florida, Cincinnati, East Carolina, Louisville, Marshall, Navy, and South Florida are charter FB members
-- SWC adds Arkansas State, Louisiana Tech, Southwestern Louisiana (later Louisiana-Lafayette), and UAB
-- WAC declines to add Rice, San Jose State, SMU, TCU, and Tulsa
2000s
-- Utah from WAC to Pac-11/12; WAC then adds Boise State and Nevada
-- Metro Conference adds Appalachian State, Buffalo, Georgia Southern, and Old Dominion
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Division I-A 1983
ACC (11): Clemson, Duke, Florida, Georgia, Georgia Tech, NC State, North Carolina, South Carolina, Virginia, Virginia Tech, Wake Forest
Big 12: Illinois, Indiana, Iowa, Iowa State, Kansas, Kansas State, Minnesota, Missouri, Nebraska, Northwestern, Purdue, Wisconsin
Big East (9): Maryland, Michigan, Michigan State, Notre Dame, Ohio State, Penn State, Pittsburgh, Syracuse, West Virginia
Pac-11: Arizona, Arizona State, California, Colorado, Oregon, Oregon State, Stanford, UCLA, USC, Washington, Washington State
SEC (8): Alabama, Auburn, Kentucky, LSU, Mississippi State, Ole Miss, Tennessee, Vanderbilt
SWC (11): Arkansas, Baylor, Houston, Oklahoma, Oklahoma State, Rice, SMU, TCU, Texas, Texas A&M, Texas Tech
WAC (9): Air Force, BYU, Colorado State, Hawaii, New Mexico, San Diego State, Utah, UTEP, Wyoming
Notable I-A Indies (15): Army, Boston College, Cincinnati, East Carolina, Florida State, Louisville, Memphis, Miami-FL, Navy, Rutgers, Southern Miss, Temple, Tulane, Tulsa, Wichita State
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Division I-A 1996
ACC (12)
Atlantic: Clemson, Miami-FL, NC State, South Carolina, Virginia, Virginia Tech
Coastal: Duke, Florida, Florida State, Georgia, Georgia Tech, North Carolina
Big 12
East: Illinois, Indiana, Minnesota, Northwestern, Purdue, Wisconsin
West: Iowa, Iowa State, Kansas, Kansas State, Missouri, Nebraska
Big East (12)
North: Boston College, Michigan, Michigan State, Notre Dame, Rutgers, Syracuse
South: Maryland, Ohio State, Penn State, Pittsburgh, Temple, West Virginia
Metro (8): Army, Central Florida, Cincinnati, East Carolina, Louisville, Marshall, Navy, South Florida
Pac-11: Arizona, Arizona State, California, Colorado, Oregon, Oregon State, Stanford, UCLA, USC, Washington, Washington State
SEC (12)
East: Alabama, Auburn, Kentucky, Mississippi State, Ole Miss, Tennessee
West: Arkansas, LSU, Oklahoma, Oklahoma State, Texas, Texas A&M
SWC (8): Baylor, Houston, Memphis, Southern Miss, TCU, Texas Tech, Tulsa, Wichita State
WAC (11): Air Force, BYU, Colorado State, Fresno State, Hawaii, New Mexico, San Diego State, UNLV, Utah, UTEP, Wyoming
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D3 Magnolia League (present day)
Emory, Johns Hopkins, Rice, SMU, Tulane, Vanderbilt, Wake Forest, Washington-MO