Answer:
- United States
- Canada
Step-by-step explanation:
As per the question, the two countries that concluded the construction of 'St. Lawrence Waterway' would be the United States, as well as, Canada. The waterway construction began in the year 1954 and took five long years and it was completed in 1959. The project was a joint venture between the U.S. and Canada which is an arrangement of several channels, waterways, and locks that allows the easy travelling of ships towards the Great Lakes located in Northern America from the Atlantic Ocean. The seaway is elongated for 595 Km beginning from Montreal to Port Colborne.