10 - The Gateway Arch: Located in St. Louis, Mo., The Gateway Arch, or the Gateway to the West, is 630 ft. tall and 630 ft. wide. It was completed in 1965. Visitors can take a tram to to top for a spectacular view of the Mississippi river and southern Illinois. Robert Harbison/The Christian Science Monitor
9 - Niagara Falls: Straddling the border between Ontario and New York, this massive waterfall can move 6 million cubic feet of water per minute during high flow. As well as being a popular tourist attraction, the falls provide hydroelectric power. The riverflow generates about 4.4 million kilowatts of electricity. Mary Knox Merrill/The Christian Science Monitor
8 - The Hoover Dam: The dam is located on the Colorado River, between the states of Arizona and Nevada. At the time of its construction in 1936, it was the world's largest hydroelectric power station. Robert Harbison/The Christian Science Monitor
7 - Mount Rushmore: This massive sculpture by Gutzon Borglum depicts former presidents George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln and hosts nearly 3 million visitors every year. The monument was intended to represent the first 150 years of American history. AP
6 - The Hollywood Sign: Located on Los Angeles's Hollywood Hills, these 45-foot tall white letters were created in 1923 as an advertisement for a housing development called Hollywoodland, but were left up. The last four letters were eventually removed. Publisher Hugh Hefner recently made news by donating $900,000 toward the purchase of land behind the sign. Reed Saxon/AP
5 - The Golden Gate Bridge: This massive suspension bridge, opened in 1937, connects the San Francisco peninsula with Marin County to the north. The bridge is internationally recognized as a symbol of San Francisco and California. Eric Risberg/AP
4 - The National Mall: This open-area park in downtown Washington D.C. hosts 24 million visitors per year and contains many well known buildings, including the Capitol Building, the Washington Monument, the Smithsonian, and the Lincoln Memorial. The Mall has been the setting for numerous rallies, protests, inaugurations, and historical events. Jacquelyn Martin/AP
3 - The Grand Canyon: This beautiful, steep-sided gorge located in Arizona is over a mile deep. Carved by the Colorado River, the canyon exposes nearly 2 billion years of geological history. Melanie Stetson Freeman/The Christian Science Monitor
2 - The Empire State Building: The tallest building in the world for over 40 years, and now the tallest in New York, the Empire State Building has been named one of the Seven Wonders of the World by the American Society of Civil Engineers. Andy Nelson/The Christian Science Monitor
1 - The Statue of Liberty: This enormous statue, officially titled Liberty Enlightening the World, commemorates the signing of the Declaration of Independence and was a gift from France in 1886. It is one of the most recognizable icons of the US and is known all around the world. Business Wire
President Obama declared almost a half-million acres of desert terrain along the U.S.-Mexico border as a national monument. Praised by environmentalists, some lawmakers in the West see Obama's move as a threat to border security.
BySusan Montoya Bryan, Associated Press
New national monument sparks border concerns President Barack Obama on Wednesday declared almost a half-million acres of rugged desert terrain along the U.S.-Mexico border as a national monument, marking the largest swath of land to be set aside for that purpose since he took office.