Like so many presidents before him, Barack Obama has invited a revered guest to his inauguration: God.

Although the Constitution forbids the government from establishing religion, faith is once again figuring prominently into the nation's grandest political pageant, just as it has over the course of American history.

Whether Republican, Democrat or Whig, presidents from the nation's beginnings have invoked the Almighty's powerful hand to convey their visions in times of calamity and contentment alike.

George Washington credited the birth of a young America to "providential agency."