I just spent a couple of evenings reading the 40th anniversary history book on Riverbanks Zoo, and at $17 U.S. the paperback version is well worth purchasing. The zoo had the youngest serving director back in the mid-1970's, and Palmer "Satch" Krantz is still leading the way almost 40 years later and he is now the longest serving zoo director in the United States. With over one million annual visitors year after year Riverbanks is actually one of the most popular 35 zoos in the country and per capita (based on its local population) it probably cracks the top 10.
Riverbanks Zoo and Garden: Forty Wild Years: Palmer "Satch" Krantz, Monique Blanchette Jacobs, Jim Maddy: 9781611173116: Amazon.com: Books
The zoo has at several points in its history undergone dramatic change in a short period of time, had a number of years of stagnancy, and then once again seen rejuvenation and renewal. There was a flurry of activity when the zoo opened in 1974, and to this day there are 5 grottoes, a siamang island and some small mammal exhibits that date from that time period. There followed 6 years of extreme financial hardship and not a lot of changes until the late 1980's. At that point the huge ARC (Aquarium-Reptile Complex) opened, along with a new entrance, gift shop and family farm. Incredibly, the zoo's attendance almost doubled in the space of 3 years!
The Botanical Garden opened in 1995 but in the decade of the 1990's there was not much in the way of animal additions. Then the period of calm came to a close as the zoo spent almost $20 million on a new entrance, Lemur Island, Bird Conservation Center, Birdhouse, Ndoki Forest (elephants, gorillas, meerkats) and other odds n' ends. Since 2002 there has been a dozen years of relative silence in terms of grand new animal exhibits, but all that is about to change as a $36 million bond issue will see yet another entrance expansion, an increase in parking, a gift shop renewal and a spectacular new sea lion habitat with underwater viewing. Future redevelopment of the 1970's-era grottoes are next on the list and while I would not agree whatsoever with the authors that Riverbanks is a "great" zoo, it is a solid one that is steadily getting better with a bright future and invaluable community support.