The Rivers of America was bleak during the 1950's. It wasn't until the early 1960's that things began looking like we would expect them to look.
Here's the Rivers of America and the Mark Twain in the spring of 1956, when Tom Sawyer Island was under construction for its Summer '56 grand opening. This is looking roughly from the current Riverbelle Terrace area, looking northwest towards what would become Critter Country 35 years later. Notice the 1950's pickup truck parked along the river, while paying customers pretend they are back in the 1870's. Oops! (And a good reminder that it took several years for Walt and his team to establish formal showmanship rules about what you should and should not do with Disneyland's daily operation)
"What about bleak?" - Auntie Mame
Here's Tom Sawyer Island in 1957 a year after it opened, taken from where the entrance of Pirates of the Caribbean is today. The future site of Star Wars Land is on the upper left side of this photo.
It wasn't until the early 1960's that enough trees had been planted, and enough seasons had gone by to fill them out a bit, that the Rivers of America took on a reasonably forested appearance. This is 1962, looking north towards Tom Sawyer Island from the present day Pirates of the Caribbean entrance.
The nice thing about the 21st century is that Disney now spends a heckuva lot of money to plant lots of mature trees right from the start, so you don't have to spend the next five years with a dusty and awkward looking environment until things start growing in.
