>>6698771 (lb)
The sources I have are mainly for tracking merchant ships to help husbanding agents and stevedoring companies. I have yet to see a track older than a week, and those are ships that are bound for Asia and get out of range of the AIS stations. The are sometimes satellite position updates but those are normally behind a paywall.
Many times I'll track ships coming in from China with stops and Korea and Japan but right after they get to Long Beach the Port Call entries get scrubbed.
If you have a specific vessel in mind I can try to back track through maybe yachting sites but I'm quite limited. I'll see if I can find online Harbor Master Logs. Any particular name you have in mind? I have tracked RHINO, SKYFALL, SEVEN SEAS, and INVICTUS before.