Walter Knott and his cousin, Jim Preston, rented land south of Buena Park and started growing berries there in 1920. They soon opened a berry stand and then a nursery to sell berry plants. The before-and-after photos above show the original berry stand around 1926 and that exact same location as it appears today.
After a while, Jim left to run his own farm in Norwalk. Then Cordelia Knott added a tea room, which eventually grew into the popular Knott's Chicken Dinner Restaurant (which turned 75 this year). Their daughter, Virginia, opened a small gift shop which grew into a large one. Walter started adding attractions to occupy visitors while they waited for a table at the restaurant. Eventually, this string of small attractions led to a larger one -- A replica of a Ghost Town, which opened to the public in 1941.
One of the earliest attractions in Ghost Town was the Wagon Train Show, in the Gold Trails Hotel, which appears in the before-and-after photos below. The older photo shows the hotel (new construction, incorporating a few pieces of buildings in actual ghost towns) in the 1940s. The "after" photo shows the recently rebuilt hotel as it appears today.
I won't give you a blow-by-blow account of all the ways Knott's Berry Farm prospered and grew. It's a pretty well known story. Suffice it to say, it was very, very successful, owing in large part to the hard work of the Knott family themselves. The photos below show a later addition to Ghost Town: The Calico Saloon. The first image shows it when it was new, around 1952, and the second image shows it as it appears today.