Designed by David B. Steinman, of Robinson & Steinman, New York City, the Waldo-Hancock suspension Bridge is a significant example of Steinman's work. David Steinman is considered among the most important suspension bridge designers of the 20th century. He earned an engineering degree from Columbia University in 1909 and went on to apprentice with Gustav Lindenthal, then at work on New York's Hell Gate Bridge. In the 1920's, Steinman emerged as an outstanding and innovative suspension bridge designer.
Sewall's Bridge is a singular example of an era when wooden trestle bridges carried highway traffic across New England waterways. It is the earliest pile-trestle bridge for which an authentic construction record exists, and the oldest for which builder's drawings survive. Spanning the York River, it was named for Major Samuel Sewall, Jr., the civil engineer who designed and constructed it.
The Portland Head Light was the first lighthouse to be constructed in Maine and the first one completed and put into service by the Federal government under the Lighthouse Act of 1789, which moved to place all lighthouses under federal control. While work had begun on the lighthouse in 1787 by the State of Massachusetts which, at that time, had jurisdiction over Maine, it was completed by the Federal government. When this lighthouse was being built, Portland was the sixth largest port in the country, the closest port to Europe and had significant trade with the Caribbean.
The Portland Observatory was built in 1807 by Captain Lemuel Moody to serve as a communication station for Portland Harbor. Portland Observatory was one of the earliest marine signal stations in the United States, and it is the last known to survive. The Observatory's location on Munjoy Hill gave it a clear view of vessels approaching Portland Harbor. The Observatory contributed to the prosperity of Portland Harbor as a vital center of maritime commerce during the "Golden Age of Sail."
Hardy fishermen and their families have long inhabited Bailey Island, which was settled in the 1720s. Ordinarily, they did not mind crossing to the mainland in their fishing boats. But before the Bailey Island Bridge was built, during certain seasons of the year when violent storms battered the coast, it was impossible to leave the island.
Maine's heavy snows led turnpike maintenance personnel to bring "left-handed" snow plows into prominence. By using left-handed and traditional right-handed plows in tandem, they were able to distribute snow more evenly - an important advance that has been emulated by many highway maintenance crews across the country.