Because of the war going on
People encountered colorful characters, lively adventures, and hometown hospitality=The canal became a popular travel experience.
Social reforms like abolitionism thrived in the canal corridor=The canal became a venue for new ideas.
Freight rates fell to just 10% of their previous cost=Merchants using the canal had dramatic profit gains.
There are many leisure activities possible in and around the canal including. . .=The canal system has a new life as venue for recreation.
The uncomfortable 2-week wagon or stagecoach trip became possible in merely 5 days=The canal revolutionized transportation.
Semicolons are used in-between two main
clauses and make a complete sentences.
If it were to be placed
after group, talking, then it also wouldn't make a sentence, So
you're right. The answer is B.