I just finished an article going into great detail on the Origin of the Catholic Church. It's s bit lengthy so I'm including a link to the page instead of copying the text into this email.
A very quick synopsis:
The inception of the Catholic Church included many pagan rituals and practices. Constantine not only allowed but encouraged many of these when he created the Church. There is a lot of evidence that he used the Church as a political move to bring unity to a failing Roman Empire.
Through the years they have introduce more and more practices and doctrines that are completely unbiblical.
The Protestant Reformation brought change but there's a reason the Great Whore of Revelation is named the "Mother of Harlots and Abominations of the earth". Read this page and find out who the daughters are and why!