* Total number of cars: The number of registered vehicles in the United States increased dramatically throughout the 1950s. While precise figures fluctuate depending on the year and source, the total number of cars was in the tens of millions.
* Car ownership per household: Car ownership wasn't universal. While it increased significantly during the decade, many families, especially lower-income ones, did not own a car. The percentage of households with at least one car rose substantially but still didn't reach 100%.
* Access to cars: Even if a household didn't own a car, many people had access to one through family, friends, or public transportation.
To get a more precise answer, you'd need to specify:
* Country: Car ownership varied greatly by country. The US had far higher rates than most other nations in the 1950s.
* Definition of "had": Did you mean owned a car outright, or had access to one?
* Specific year: The number of cars and car ownership rates changed year by year throughout the decade.
In short, millions of people had cars in the 1950s, but it was far from universal ownership. To give you a more specific number, I'd need more details.
