Under a bill that passed the Missouri House on Tuesday, voters in St. Louis and St. Louis County will be able to decide whether to further fund the city's zoo via a sales tax increase.

But, originally, the tax burden — an increase of one-eighth of 1 percent — would have been shared by surrounding counties as well. That option was stripped in both House Bill 935 and Senate Bill 49 for simplicity's sake, according to legislators.

The zoo, which is free for all visitors, received about $21 million in 2015 from the Zoo-Museum District property tax that's levied in St. Louis and St. Louis County. Earlier versions of House Bill 935 included St. Charles, Franklin, and Jefferson counties as part of the new proposed tax, and would have created a commission made up of the four counties and St. Louis.

“We just thought that would be the simpler way to get this done but still limit the amount of money that could be taxed for this purpose," said Rep. Marsha Haefner, a Republican from Oakville who sponsored the House bill.

The Senate's version received first-round approval last week and is scheduled for another vote Thursday. Democratic floor leader Gina Walsh of Bellefontaine Neighbors, who is sponsoring the bill, said she took out the other counties in order to “garner more support from other legislators.”

Opponents in the House, including Democrat Tracy McCreery of Olivette, said another sales tax would place an extra burden on homeowners.

“In a way, it’d be like I’m being double-taxed, so I’m paying for the zoo not only through my personal property tax, but now you want to tax us through a sales tax,” she said. “How many more taxes are St. Louis County residents and homeowners going to pay until we say ‘enough is enough?’”

Earlier this month, county voters approved a half-cent sales tax increase for policing and public safety purposes.

Haefner said McCreery's concern is addressed by a provision that keeps the total combined rate of locally passed sales taxes from exceeding 1 percent.

Another piece of the House bill allows the St. Louis Zoo to charge admission to city and county residents if the sales tax measure doesn't pass, but only for “zoological facilities, programs, or events” that aren't on the zoo grounds.

Zoo president and CEO Jeffrey Bonner testified in March that the organization spending $2 million annually on infrastructure, much of which is deteriorating due to age. The St. Louis Zoo opened in 1904.

Follow Marshall Griffin on Twitter: @MarshallGReport