Container Vessel Dwell Times

In late 2020 and early 2021, due to port congestion, many vessels waited at anchorages in San Pedro Bay, California, and elsewhere for port access to load and unload containerized cargo. In late December 2021, the ports of Los Angeles and Long Beach had 91 container vessels waiting to berth, spending in some cases, many more days at anchor than at dockside. In total, U.S. container ports had about 112 container vessels at anchor waiting to berth on December 21. [1] 
The average container vessel dwell time at the top 25 U.S. container ports[2] was estimated at 28.1 hours in 2020, down slightly from 28.2 hours in 2019. Overall, as shown in the figure below, dwell times for container vessels fluctuated monthly, with dwell times increasing steadily throughout the latter half of 2020. Prolonged dwell times can reduce the number of vessel calls a port can handle. 
In the first half of 2021, average container vessel dwell times increased to 31.5 hours. The top 25 container ports had 6,537 observed vessel calls, down 1,825 (21.8 percent) from the same period in 2020 despite the overall economic growth in the period indicated by increases in GDP.[3]
Average container vessel dwell times for individual ports are shown in the online Port Profiles.  
Footnotes
[1] U.S. Department of Transportation, Maritime Administration, Office of Policy and Plans/Marine Exchange of SoCal, Special Tabulation, as of December 2021.
[2] The top 25 container ports are based on 2020 port rankings provided by the U.S. Army Corps of Engineer, Waterborne Commerce Statistics Center as of December 2021.
[3] The top 25 container ports are based on 2020 port rankings and calculated using 2021 AIS data from the sources cited above.