George Mason was the principal author of the Virginia Declaration of Rights in 1776. A part of this document, along with other documents, served as a model for the first section of the Declaration of Independence and the federal Bill of Rights. From 1776-1788 Mason served in the Virginia House of Delegates. He attended the Constitutional Convention in 1787, where he was a leader in framing the new government. He was a slave owner and opposed the section of the proposed constitution that allowed the slave trade to continue until 1808. Mason became an active and articulate opponent of the U.S. Constitution, largely because he believed it vested too much poorly defined power in the national government. He refused to sign the document and voted against it in the Virginia Ratifying Convention of 1788.