Which TV network originally aired 'I Love Lucy'?

Which TV network originally aired 'The Walking Dead'? Which TV network originally aired 'The Big Bang Theory'? Which TV network originally aired 'Grey's Anatomy'? Which TV network originally aired 'Cheers'? Which TV network originally aired 'M*A*S*H'? Which TV network originally aired 'Lost'? Which TV network originally aired 'The X-Files'? Which TV network originally aired 'South Park'?