A quote early in On the Road that really struck me was before Sal had made it out of New York. He is looking at the Hudson River and he says "If you a drop a rose in the Hudson River at its mysterious source in the Adirondacks, think of all the places it journeys by as it goes out to sea forever..." Immediately this struck me as analogous to Sal's journey and it was in my mind for the whole first part of the book. This quote is relevant to Sal's experience for two reasons. First, it emphasizes the importance of each individual stop along his journey. Second, by saying it "goes out to sea forever" it hints that once Sal begins his journey it really never ends.
Each individual place he stops at is important to his journey whether he feels he has a good experience or not. Whether it's a group of college kids picking him up while they talk about their exams, or a seedy looking man offering him a job as a Carny, everything is an experience and changes him in some way. Even just standing in the rain in the middle of nowhere while he curses himself and threatens to give up his quest out west is an experience to be learned from. He has time to reflect on his own thoughts and learn more about himself. He also can appreciate compassion and humanity more when a generous person finally stops to pick him up and rescue him. Like the rose dropped into the river, he slowly gets withered and changed by each place he winds into, and eventually it is hard to see where he originally came from.
Later in the book when his hitchhiking journey out west technically is completed, his traveling never stops. In California he is already making plans to go back to New York, and after that plans to travel once again. In this first half of the book, Sal realizes that his home might actually be on the road. He appears to idolize people like Old Bull Lee because of their many experiences, and Sal desires a similar lifestyle. Sal has left his mysterious source and seems destined to journey outward forever.