Why did Mark Twain right Huckleberry Finn?

Can you enlighten me on the motivations behind Mark Twain's decision to pen the masterpiece known as Huckleberry Finn? Was it a personal experience that inspired him, or did he aim to convey a particular message through the tale? I'm intrigued to know what drove him to create such a captivating and thought-provoking work that continues to resonate with readers across generations.