Final answer:
The treaty signed by Canada and the United States meant to help control pollution along a portion of their shared border is not explicitly stated, but agreements such as the Migratory Bird Treaty Act of 1918 and the Pollution Prevention Act of 1990 are examples of US legislation with environmental focus that could influence bilateral strategies. The Montreal Protocol is an international agreement that involved both countries.
Step-by-step explanation:
The treaty signed by Canada and the United States meant to help control pollution along a portion of their shared border is not specifically detailed in the historical accounts provided. However, the Migratory Bird Treaty Act (MBTA) of 1918 is one such agreement between the two countries that dealt with environmental conservation by protecting over 800 species of birds. While it focused on the conservation of migratory birds rather than pollution control per se, it represents an early form of bi-national cooperation on environmental issues. If the student is referring to more modern agreements, they may be thinking of the Pollution Prevention Act of 1990, which although a U.S. law, set a precedent for collaborations between states, tribes, and communities in pollution prevention strategies that could be applied to transboundary issues. Also worth noting are international environmental agreements like the Montreal Protocol of 1987 for the protection of the ozone layer, which, while not specific to the US-Canada border, involved both nations and had worldwide environmental impact.