From the OKC Zoo website;

On Saturday, July 17, admission to the Oklahoma City Zoo is FREE for everyone! In recognition of the 1/8 cent sales tax passed by the citizens of Oklahoma City on July 17, 1990, the Zoo is saying "Thank you!" to Oklahoma City with free admission. The Zoo will be open from 8 a.m. to 8 p.m. on Saturday, with exhibit buildings closing at 7:45 p.m. Sea Lion Show times for Saturday are 10:30 a.m., 1 p.m. and 3 p.m.

Thanks for the post. I usually try to walk the zoo during free Mondays in December through February. I will likely be there at 9 am tomorrow for my morning walk so I can beat the heat.

From the OKC Zoo website;

On Saturday, July 17, admission to the Oklahoma City Zoo is FREE for everyone! In recognition of the 1/8 cent sales tax passed by the citizens of Oklahoma City on July 17, 1990, the Zoo is saying "Thank you!" to Oklahoma City with free admission. The Zoo will be open from 8 a.m. to 8 p.m. on Saturday, with exhibit buildings closing at 7:45 p.m. Sea Lion Show times for Saturday are 10:30 a.m., 1 p.m. and 3 p.m.

That's a really good PR move for them. I wish it had been more heavily publicized. In spite of some occasional problems the OKC Zoo is a treasure that most cities would be thrilled to have.