The US city that fits this description is Boston, Massachusetts. Boston is the capital city of Massachusetts and home to the Massachusetts State House, which serves as the state's capital building. It is located on the east coast of the United States, allowing visitors to see the Atlantic Ocean.
While Boston itself is not on the Pacific Ocean, driving for approximately an hour west from Boston would take you to the state of Massachusetts' western border. From there, you could continue driving west to reach the Pacific Ocean, although it would take several days as the distance is significant.
As for the 17th-century architecture, Boston has a rich history and is known for its preservation of historic buildings. The city has several areas, such as the Beacon Hill neighborhood and the Freedom Trail, where you can see well-preserved examples of 17th-century architecture, including the famous Paul Revere House and the Old North Church.