Gov. Dennis Daugaard is asking that all flags in the state be flown at half-staff on Tuesday in honor of those who lost their lives in terrorist attacks of Sept. 11, 2001.
The flags are to be lowered from 8 a.m. until sunset.
The White House has issued a proclamation designating Tuesday as Patriot Day and a national day of service and remembrance.
President Barack Obama will mark the 11th anniversary of the attacks with a series of commemorations in and near Washington.