In-N-Out Burger's first location was opened in the suburb of Baldwin Park, California, in 1948 by the Snyders. The restaurant was the first drive-thru hamburger stand in California, allowing drivers to place orders via a two-way speaker system.  This was a new and unique idea, since in post-World War II California, carhops were used to take orders and serve food

The signature colors for In-N-Out are white, red, and yellow. The white is used for the buildings' exterior walls and the employees' basic uniform. Red is used for the buildings' roofs and the employees' aprons and hats. Yellow is used for the decorative band on the roof and iconic arrow in the logo. However, variations in the color scheme do occur.

The first In-N-Outs, like Store #10, had a common design, placing the kitchen "stand" between two lanes of cars. The "front" lane is nearest the street and the "back" lane away from the street. This location design is known as a double drive-thru. A metal awning provides shade for several tables for customers desiring to park and eat, but there is no indoor dining. A walk-up window faces the parking area. These restaurants store food and supplies in a separate building, and it is not uncommon for a driver to be asked to wait a moment while employees carry supplies to the kitchen across the rear lane.

The chain also has fans in several chefs including Gordon Ramsay, Thomas Keller, Julia Child, Anthony Bourdain, Ina Garten, and Mario Batali.  Famous London chef/restaurateur Ramsay ate In-N-Out for the first time when taping Hell's Kitchen in Los Angeles, and it soon became one of his favorite spots for take-out.   Ramsay was quoted, saying about the experience: "In-N-Out burgers were extraordinary. I was so bad, I sat in the restaurant, had my double cheeseburger then minutes later I drove back round and got the same thing again to take away."

Julia Child, one of the first celebrities to champion the chain, admitted to knowing every location of the restaurant between Santa Barbara and San Francisco.  Anthony Bourdain reportedly said that In-N-Out was his favorite fast-food meal, later naming the restaurant as "the best restaurant in Los Angeles".