As the country ramps up vaccination efforts in the war against the coronavirus, scientists and medical professionals agree the goal for America is to reach heard immunity to beat  the virus. An estimated 70% of Americans will need to be vaccinated to achieve this goal, in order for the United States to confidently reopen without falling back into another resurgence. Some countries are considering specials travel passports. Is this the answer? If so, what would they look like?

Most people are asymptomatic and show no signs of being infected with the coronavirus. How will we know who's been vaccinated and who hasn't? Furthermore, how will travelers know it's safe to vacation if there is no protocol or proof other travelers aren't sick with the virus? It's becoming more and more apparent that some type of documentation will eventually need to be established to provide proof we are safe to be around one another. What will this so-called clean bill of health proof look like? Are we going to need vaccine passports?

LOOK: Stunning vintage photos capture the beauty of America's national parks

Today these parks are located throughout the country in 25 states and the U.S. Virgin Islands. The land encompassing them was either purchased or donated, though much of it had been inhabited by native people for thousands of years before the founding of the United States. These areas are protected and revered as educational resources about the natural world, and as spaces for exploration.

Keep scrolling for 50 vintage photos that show the beauty of America's national parks.