Col. Jim Keathley announced his plans to retire in March after more than three years as leader of the state Highway Patrol.
Keathley began as a trooper 33 years ago.
Keathley made his announcement in the office of a clearly saddened Gov. Jay Nixon.
"It will be hard to see a good friend go," Nixon said.
The governor did not name a replacement.
Legislative leaders cited ethics reform and the state's budget as the top priorities for the 2010 session that began Wednesday at noon.
The session was marked by the progress of three former legislators through the criminal justice system -- one who learned his sentence on a federal bribery charge, another who was scheduled to appear in court on assault charges and a third who began his second day in federal prison on a justice obstruction charge.
The state's budget director reported Tuesday that state revenue collections for the month of December fell 21.7% below collections for December of 2008.
For the first half of the fiscal year, that began July 1, revenue collections are 10.6 behind the prior fiscal year.
The latest revenue figures were reported on the eve of the legislature's 2010 session -- a session in which legislative leaders have predicted that budget problems would be the top issue for state lawmakers.
In a five-hour hearing before a Senate environmental committee, witnesses provided testimony to the reasoning behind the Department of Natural Resources's decision to withhold information about elevated E. coli levels in the Lake of the Ozarks.
According to DNR lab staffer Scott Robinett, it isn't unusual to withhold test results before a press release is drafted. But Robinett did say the delay in this particular case was much longer than the usual two week period.
There was partisan debate from members of the committee. The committee Vice Chairman, Republican Senator Kurt Schaefer, said there was no reason the public shouldn't have been informed about the levels, even if the DNR was waiting to analyze the results.
But Democratic member Joan Bray pointed out the results could have been irrelevant because so many factors like rain and wind can alter the results on a daily, or even hourly basis - which is why analysis is often needed.
Former DNR Deputy Director Joe Bindbeutel, who was dismissed after admitting to withholding information, also testified Tuesday. He admitted to withholding information about elevated E. coli levels, but defended his decision saying a plan of action needed to be in place before a public announcement could be made.
Legislative leaders and the governor have agreed upon a revenue estimate that projects an historic decline in state revenues for the current fiscal year.
On Monday, the legislative budget leaders and governor agreed upon a "consensus revenue estimate" that projects the state will collect $480 million less during the current fiscal year than last year.
According to the governor's office, it is the "only year in modern history where revenues have fallen at a faster pace."
For the next fiscal year, that begins July 1, they estimate just a 3.6 percent increase in state General Revenue collections.