Final answer:
Medical insurance plans covering various health care procedures began to be offered in the mid-20th century, with significant expansions such as Medicare in 1965 and the ACA in 2010.
Step-by-step explanation:
Medical insurance companies began offering medical plans that would cover the costs of routine, preventive, and emergency health care procedures notably around the mid-20th century. One of the earliest examples of this kind of coverage was started by Flint Goodridge Hospital in New Orleans in 1936, providing low-cost insurance for working-class individuals.
However, the most significant expansion of health coverage came with the legislation of Medicare in 1965, which was a federal system of health insurance for the elderly, covering most hospital bills (Plan A) or functioning much like an employer's health plan (Plan B). The passage of the Patient Protection and Affordable Care Act (ACA) in 2010 marked another important milestone by increasing Medicaid eligibility and ensuring coverage for people with pre-existing conditions, among other provisions.