What Influenced John Steinbeck to Write "Of Mice and Men"?

In the book, the two main characters are George Milton and Lennie Small. They are two displaced migrant ranch workers living during the Great Depression. They go from place to place around California in search of employment opportunities. Steinbeck lived a similar life. He was a bindlestiff, or a homeless person who carries his belongings wrapped in cloth and tied around a stick, in the 1920s. The title of the book comes from a poem by Robert Burns called "To a Mouse."