What is the history and purpose of observation units in emergency medicine?

Observation units were initially designed to park patients until a hospital bed was available or until a family member could pick them up.
The current observation units are active areas with rapid evaluation and treatment, where reevaluation is continuous and analysis of results is ongoing.
The cost of evaluating and treating patients in observation units is estimated to be half of what it would cost to hospitalize them.
Observation units have been shown to be cost-effective and safe alternatives to conventional hospitalization for certain medical processes.