As highlighted by @Bkay, these linked documents are likely to rot. For future users, the keyword I was missing when searching for these documents was 'tariff schedule'. The below links to 2019 tariff schedules. I suggest that in the future a user search:
'YEAR tariff schedule COUNTRYOFINTEREST'
It may also be useful to specify the trade agreement of interest.
For USA: Harmonized Tariff Schedule 2019 Revision 2
For Canada: Customs Tariff by Chapter (Customs Tariff 2019-1)
For Mexico (and all three): Mexico Import Export Codes
Chapters of interest will vary by personal use.