Arches National Park is one of 401 National Park Service sites to close to visitors during the government shutdown.
Wildlife will be roaming in visitor-free peace at Yellowstone National Park -- the fourth-most-visited national park in 2012, with 3.4 million visitors last year.
New York's Statue of Liberty, one of the United States' most recognizable symbols, is among the National Park Service sites affected by the federal government shutdown. This means Liberty Island, a national park, is closed to visitors too.
Washington's Olympic National Park is famous for offering visitors ocean, mountains and rain forest in one park. Now that the U.S. government shutdown has come into effect, guests staying in campgrounds and on-site hotels will be given 48 hours to leave.
Tennessee's Great Smoky Mountains National Park, a UNESCO World Heritage Site, is the nation's most visited with 9.7 million visitors last year. The shutdown comes as the park enters one of its busiest months of the year, according to visitor stats.
Nearly 2.5 million people visited Maine's Acadia National Park last year. Mid-October is usually a busy time of year, with travelers coming in to check out the colorful fall leaves in the forests.
A passenger removes their shoes before passing through the passenger security checkpoint at John F. Kennedy International Airport in New York City. Airport security personnel are considered essential and will continue working through the shutdown.
The Normandy American Cemetery and 23 other overseas cemeteries operated by the American Battle Monuments Commission will be closed to the public for the duration of the shutdown.
Air traffic controllers, some safety inspectors and other essential employees will "continue working in order to maintain the safety of the national airspace system," said the Federal Aviation Administration.
Congress and the president are facing off in another supreme spending showdown. If they don't agree on a funding bill by the end of September 30, much of government will shutdown.
President Barack Obama. Expect the president to use his podium more as a shutdown nears, aiming at public opinion as Democrats in Congress position themselves.
Rep. Mark Meadows, R-North Carolina. During Congress' August recess, the tea party-backed freshman wrote to Republican leaders suggesting that they tie dismantling Obamacare to the funding bill.
Speaker John Boehner, R-Ohio. He'll make the key play call. Boehner could decide whether to push through the Senate's version of a spending bill and keep government running, or float a third version with some other Republican wish list items in it.
Sen. Ted Cruz, R-Texas. The revolutionary or rabble rouser, depending on your viewpoint. Cruz has stoked the anti-Obamacare flames all summer, but recently angered fellow Republicans by openly saying the Senate does not have the votes to repeal the law.
Sen. Marco Rubio, R-Florida. The potential presidential candidate has been one of three senators (Cruz and Mike Lee, R-Utah, being the others) pushing to use the government shutdown debate as a way to repeal or defund Obamacare.
Sen. Harry Reid, D-Nevada. The main force in controlling the voting process in the chamber, Reid will be a primary negotiator if the House does not accept the Senate spending bill.
Sen. Mitch McConnel, R-Kentucky. The Republican leader & several of his members say they will vote against Cruz's filibuster in favor of a bill that just funds government. McConnell generally has been leery of running into a shutdown or default.
Rep. Peter King, R-New York. King is pushing for Republicans to accept a more "clean" spending bill that can pass the Senate and avoid a shutdown.
Thomas Donohue, president and CEO of the U.S. Chamber of Commerce. The Chamber is an important political backer for conservatives, but has had mixed success with the current Congress.
Michael Needham, president of Heritage Action. Needham has been unrelenting in urging lawmakers to repeal Obamacare. He has told Republicans not to fear a potential shutdown, saying they would suffer more politically from allowing Obamacare to continue.
Rep. Eric Cantor, R-Virginia. The House Republican No. 2 is much more closely allied with conservatives and tea party members in the House than is Speaker Boehner.
Rep. Nancy Pelosi, D-California, and Steny Hoyer, D-Maryland. The top two House Democrats are mostly watching and waiting. They could either bring Democratic votes on board a deal or be the loudest voices against a new Republican alternative.
Rep. Paul Ryan, R-Wisconsin. The vote of the House budget chairman and former vice presidential nominee is an important signal both within Republican ranks and to the public at large.