Poplar Bluff voters approved a one-half cent sales tax in 2005 to pay for 50 miles of highway improvements.
The money created a four-lane highway between Poplar Bluff and Fredericktown.
The tax was not expected to generate the full $43.6 million cost owed by the city of Poplar Bluff until 2035. This represents just under 28 percent of the full $159.7 million project.
Officials with the Missouri Department of Transportation now expect that target to be reached by 2020.
The city has been making principal and interest payments of between $2 million and $2.4 million each year since 2007, according to financial information presented last week at a Highway 67 Corporation meeting. The final three payments -- in 2018, 2019 and 2010 --will be closer to $3 million each.
Poplar Bluff's payments to the project represented the largest single contribution.
Federal money made up $40.8 million or almost 26 percent, while the U.S. Army Corps of Engineers funded $27.9 million. The state contributed $21.8 million, about 14 percent, and another $19.9 million came from earmarks. The final $5.6 million was paid by the Delta Regional Authority, an agency set to be eliminated under an initial federal budget from President Donald Trump.