How did chicken sandwiches become so popular in the U.S.? Supply and demand. The emergence of large scale chicken processing companies such as Perdue and Tyson in the 1920’s and 1930’s respectively, helped propel chicken’s popularity in America. With such easy availability, chicken prices decreased, consumption increased, and chicken became a steady part of the American diet.
With many families cooking whole chickens, leftovers became standard lunch fare. Sliced leftover chicken meat became a favorite filling for sandwiches (and was the original filling for the classic club sandwich).
Fast food chicken sandwiches as we know them originated in 1967, when Truett Cathy, founder of the Atlanta based restaurant chain Chick-fil-A, introduced the chicken sandwich -- a perfectly crispy-on-the-outside, juicy-on-the-inside breaded boneless breast of chicken served on a toasted buttered bun with dill pickle chips. Whether it's fact or fiction, Cathy claimed that pickles were the only condiment he had on hand, and to his delight, were a big hit with consumers. Other fast food chains quickly followed suit. Then in the late 1980's and early '90's the grilled chicken sandwich emerged as a healthier alternative to the fried original.

“I’m hungry. Can someone please help me? Please. This is serious. I haven’t eaten since early this morning. Please.” The plea came from a diminutive man I had just rushed passed on 8th Avenue in New York City. He was wearing a grey cap pulled down over his forehead and held a tattered white plastic shopping bag. It was 12:30 a.m. A hard March wind was blowing through Chelsea and everyone who passed this pleading man, was hurrying to someplace warm, including me. 
My family likes sandwiches. My present husband had his bachelor party at Langer’s. The day before our wedding, while I was at a ladies’ lunch thrown by my sisters, my husband, his son, my son, his daughter’s boyfriend, my brother-in-law, and one of my nephews went to Langer’s Deli (across the street from MacArthur Park) and ordered pastrami sandwiches, lots of them, I understand, more than one apiece. And it was further evidence to me that I was marrying the right person.
A Monte Cristo consists of ham, turkey or chicken, and Swiss cheese sandwiched between two slices of white or challah bread that is dipped in an egg batter, then grilled or fried in butter until golden brown. It is often dusted with confectioners’ sugar and served with a side of red currant jelly.
My dad was a two job guy. We lived in a representative, working class
neighborhood in Brooklyn, which was to me, the paradise of the world.
Representative I learned years later meant not just Jewish people, like
us, but an equal mix of almost everything else. The working class is
obvious.