Notre Dame, college football’s most popular independent program, will join the A.C.C. for five games per year starting in 2014.

Missouri and Texas A&M were the first teams to join the SEC in 20 years.

No college has left the SEC, the Pac-12 or the Big Ten for another conference in the modern era. Placement in these elite conferences virtually guarantees national exposure.

Unlike the more localized Big East, the American covers half the country, with some colleges more than 1,500 miles apart.

Boise State left for the Mountain West in 2010. Three years later, the WAC folded.

A Supreme Court ruling in 1984 let universities and conferences negotiate their own television deals. ESPN aired its first live regular-season game that fall.

Penn State, one of the last major programs to remain independent, became the Big Ten’s 11th member in 1993, setting off a wave of realignment across college football.

Arizona and Arizona State made the Pac-8 the Pac-10.

The Ivy League joined Div. 1-AA.

Formed as a basketball-only conference, the Big East began playing football in part to stay competitive.

Arkansas departured for the SEC in 1991 signaled the beginning of the end for the Southwest Conference, long associated with NCAA violations.

The Southern Conference reclassified to Div. 1-AA.

The Missouri Valley Conference stopped sponsoring football.

In 1988, the Pacific Coast Conference changed its name to the Big West.

Financial benefits and concerns about conference stability lured Boston College, a founding member of the Big East Conference, to become the A.C.C.’s 12th member in 2005.