Puente de las Americas

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that all serve unique purposes and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed, the material used to make it and the funds available to build it.

The Bridge of the Americas (Spanish: Puente de las Américas; originally known as the Thatcher Ferry Bridge) is a road bridge in Panama, which spans the Pacific entrance to the Panama Canal. Completed in 1962, at a cost of US$20 million, it was the only non-swinging bridge (there are two other bridges, one at the Miraflores locks and one at the Gatun locks) connecting the north and south American land masses until the opening of the Centennial Bridge in 2004. The bridge was designed by Sverdrup & Parcel.

Central America (Spanish: América Central or Centroamérica) is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent. Central America consists of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Central America is part of the Mesoamerican biodiversity hotspot, which extends from northern Guatemala through central Panama. It is bordered by Mexico to the north, the Caribbean Sea to the east, the North Pacific Ocean to the west, and Colombia to the south-east.

Central America is an area of 524,000 square kilometers (202,000 sq mi), or almost 0.1% of the Earth's surface. As of 2009, its population was estimated at 41,739,000. It has a density of 77 people per square kilometer.

Middle America is a region in the mid-latitudes of the Americas. In southern North America, it usually comprises Mexico, the nations of Central America, and the Caribbean. The scope of the term may vary. Sometimes, Colombia and Venezuela are also included in Middle America; the Caribbean are occasionally excluded from the region; and the Guianas are infrequently included.

Physiographically, Middle America marks the territorial transition between the rest of North America and South America, connecting yet separating the two. On the west, the Middle American mainland comprises the tapering, isthmian tract of the American landmass between the southern Rocky Mountains in the southern United States and the northern tip of the Andes in Colombia, separating the Pacific Ocean on the west and the Atlantic Ocean (viz. the Gulf of Mexico and Caribbean Sea) on the east, while the Greater and Lesser Antilles form an island arc in the east. The region developed sub-aerially southward from North America as a complex volcanic arc-trench system during the Early Cretaceous period, eventually forming the land bridge during the Pliocene epoch when its southern end (at Panama) collided with South America through tectonic action.

The Panama Canal (Spanish: Canal de Panamá) is a 48-mile (77.1 km) ship canal in Panama that connects the Atlantic Ocean (via the Caribbean Sea) to the Pacific Ocean. The canal cuts across the Isthmus of Panama and is a key conduit for international maritime trade. There are locks at each end to lift ships up to Gatun Lake (85 feet (26 m) above sea-level). The Gatun Lake was used to reduce the amount of work required for a sea-level connection. The current locks are 110 feet (33.5 m) wide. A third, wider lane of locks is being built.

France began work on the canal in 1881, but had to stop because of engineering problems and high mortality due to disease. The United States (US) later took over the project and took a decade to complete the canal in 1914, enabling ships to avoid the lengthy Cape Horn route around the southernmost tip of South America (via the Drake Passage) or to navigate the Strait of Magellan. One of the largest and most difficult engineering projects ever undertaken, the Panama Canal shortcut made it possible for ships to travel between the Atlantic and Pacific Oceans in half the time previously required. The shorter, faster, safer route to the US West Coast and to nations in and along the Pacific Ocean allowed those places to become more integrated with the world economy.

During this time, ownership of the territory that is now the Panama Canal was first Colombian, then French, and then American; the United States completed the construction. The canal was taken over in 1999 by the Panamanian government, as long planned. Annual traffic has risen from about 1,000 ships when the canal opened in 1914, to 14,702 vessels in 2008, the latter measuring a total of 309.6 million Panama Canal/Universal Measurement System (PC/UMS) tons. By 2008, more than 815,000 vessels had passed through the canal, many of them much larger than the original planners could have envisioned; the largest ships that can transit the canal today are called Panamax. The American Society of Civil Engineers has named the Panama Canal one of the seven wonders of the modern world.