The framers of the Constitution knew it would be necessary to add provisions or make revisions to the original document. To date, there have been twenty-seven of these additions or revisions.

The framers of the United States Constitution designed the document to be a living, adaptable instrument of governance. They realized that as times changed, so too would the needs of the nation, and that the Constitution might require amendments to address these evolving circumstances.

To address this need, they included an amendment process within the Constitution itself, as laid out in Article V. This process allows for amendments to be proposed and ratified, thereby making formal changes to the Constitution.

Since the Constitution went into effect in 1788, there have indeed been twenty-seven amendments added to it. The first ten amendments, known as the Bill of Rights, were ratified in 1791 and guaranteed fundamental rights and protections to American citizens. Subsequent amendments have addressed a range of issues including extending voting rights, modifying presidential term limits, and clarifying succession, among others.

Amendments to the U.S. Constitution are proposed in one of two ways: by a two-thirds majority vote in both houses of Congress or by a convention called for by two-thirds of state legislatures. To be ratified, proposed amendments must then be approved by three-fourths (currently 38 of 50) of the state legislatures or by conventions in three-fourths of the states. This makes the amendment process intentionally difficult, reflecting the framers’ desire that constitutional changes be considered and supported by a substantial majority.

Extra: The process of amending the Constitution is a testament to the foresightedness of its framers. In recognizing the need for a way to make changes, they ensured that the Constitution would remain relevant as the country grew and changed. Nevertheless, the difficulty of the amendment process reflects the importance of stability and continuity in the nation's fundamental laws. The amendments themselves cover a wide range of issues. Some of the most significant include:

- The 13th Amendment (1865), which abolished slavery. - The 14th Amendment (1868), which granted citizenship to all persons born or naturalized in the United States and provided for equal protection under the law. - The 15th Amendment (1870), which prohibited denying the right to vote based on race, color, or previous condition of servitude. - The 19th Amendment (1920), which gave women the right to vote. - The 22nd Amendment (1951), which limited the presidential term to two terms. - The 26th Amendment (1971), which lowered the voting age to 18.

Each amendment has its own history and reasons for being adopted, often reflecting the social and political forces at play at the time of their proposal and ratification. The Constitution, with its amendments, has thus served as a stable foundation for U.S. government and law, ensuring that the rights of citizens are protected and that the structure of the government can adapt to the changing needs of the nation.