Panama Canal

===Lock size===
{{Main|Panama Canal locks}}Because of the importance of the canal to international trade, many ships are built to the maximum size allowed.[[File:Gatun lock gate.JPG|thumb|right|upright|Miter [[Lock (water transport)|lock]] gate at Gatún]]

For its first century, the width and length of ships that may transit the canal was limited by the Pedro Miguel Locks; their [[Draft (hull)|draft]] by the canal's minimum {{convert|41.2|ft|m|abbr=on|order=flip}} depth; and their height by the main span of the Bridge of the Americas at Balboa. Ships built to those limits are known as [[Panamax]] vessels. A Panamax cargo ship typically has a [[deadweight tonnage]] (DWT) of 65,000–80,000 [[tonnes|tons]], but its actual cargo is restricted to about 52,500 tons because of the canal's [[Draft (hull)|draft]] restrictions within the canal.<ref>{{cite web |url=http://www.lr.org/Images/30%20ship%20sizes_tcm155-173543.pdf |title=Infosheet No. 30: Modern ship size definitions |date=26 July 2007 |url-status=dead |archive-url=https://web.archive.org/web/20120224003817/http://www.lr.org/Images/30%20ship%20sizes_tcm155-173543.pdf |archive-date=2012-02-24 |work=Lloyd's Register}}</ref> The longest ship ever to transit the canal was the ''San Juan Prospector'' (now ''Marcona Prospector''), an [[ore-bulk-oil carrier]] that is {{convert|973|ft|m|2|abbr=on|order=flip}} long with a [[beam (nautical)|beam]] of {{convert|106|ft|m|2|abbr=on|order=flip}}.<ref>{{Cite web |title=Professional Resources in Science and Mathematics (PRISM) |url=https://www.montclair.edu/prism/ |access-date=2023-05-01 |language=en-US}}</ref>

Initially the locks at Gatun were designed to be {{convert|28.5|m|ft|abbr=on}} wide. In 1908, the [[United States Navy]] requested that the width be increased to at least {{convert|36|m|ft|abbr=on}} to allow the passage of large warships. A compromise was made and the locks were built {{convert|33.53|m|ft|abbr=on}} wide. Each lock is {{convert|320|m|ft|abbr=on}} long, with the walls ranging in thickness from {{convert|15|m|ft|abbr=on}} at the base to {{convert|3|m|ft|abbr=on}} at the top. The central wall between the parallel locks at Gatun is {{convert|18|m|ft|abbr=on}} thick and over {{convert|24|m|ft|abbr=on}} high. The steel lock gates measure an average of {{convert|2|m|ft|abbr=on}} thick, {{convert|19.5|m|ft|abbr=on}} wide, and {{convert|20|m|ft|abbr=on}} high.<ref>{{cite web
|url=http://www.eclipse.co.uk/~sl5763/panama.htm
|title=The Panama Canal
|access-date=2007-10-18
|archive-url=https://web.archive.org/web/20080515050735/http://www.eclipse.co.uk/~sl5763/panama.htm
|archive-date=May 15, 2008
|url-status=dead
}}</ref>

Panama Canal pilots were initially unprepared to handle the flight decks of [[aircraft carrier]]s, which protrude beyond the hull on either side of the ship. When {{USS|Saratoga|CV-3|6}} made her first trip through the Gatun Locks in 1928, the ship knocked over all the concrete lamp posts along the canal.<ref>{{cite journal |last=Pride |first=Alfred M. |year=1986 |title=Pilots, Man Your Planes |journal=Proceedings |volume=Supplement |issue=April |pages=28–35 |publisher=[[United States Naval Institute]] }}</ref>

In 2016, a [[Panama Canal expansion project|decade-long expansion project]] created larger locks, allowing bigger ships to transit through deeper and wider channels.<ref name="AP 2016" /> The allowed dimensions of ships using these locks increased by 25 percent in length, 51 percent in beam, and 26 percent in draft, as defined by [[Panamax#New Panamax|Neopanamax]] metrics.<ref>{{cite web
|url=http://www.pancanal.com/common/maritime/advisories/2009/a-02-2009.pdf
|title=New Panamax publication by ACP
|date=November 2006
|access-date=2010-10-24
|archive-url=https://web.archive.org/web/20090506230338/http://www.pancanal.com/common/maritime/advisories/2009/a-02-2009.pdf
|archive-date=May 6, 2009
|url-status=dead
}}</ref>