Missouri was the first state in the nation to have direct experience with all three methods of judicial selection.

Missouri's first constitution provided the state's judges would be nominated by the governor, with advice and consent of the senate, and could hold office "during good behavior" until the age of 65. The 1820 Constitution allowed the legislature to ask the governor to remove any judge from office with a two-thirds vote of each chamber. 

But during the 1830s and 1840s, the public became concerned that the legislatures to which the courts essentially were subordinate were too powerful and beholden to special interests. In what became known as Jacksonian Democracy, states began moving away from gubernatorial appointment and toward popular election. Missouri followed suit in 1850, adopting judicial selection by direct partisan elections. The 1850 Constitution also set the judges' terms at six years, just half the length of the 12-year terms for Supreme Court judges the legislature had prescribed in 1847. 

Before long, however, people became concerned about the influence of political parties over their courts. It was no different in Missouri, where politics by the early 20th century were controlled by Democrats. The most notorious political machine was controlled by "Boss" Tom Pendergast of Kansas City, who sought to exert control over judicial elections and, therefore, the judiciary itself. In addition, ward bosses largely controlled judicial elections in St. Louis, where a pharmacist with a law degree but no experience as an attorney was elected to be a circuit judge.

In response, a statewide citizen's committee was organized, ultimately recommending the state adopt a nonpartisan court plan for selecting judges. Such a plan, based on what became known as "merit selection," had been advocated by lawyers and scholars nationally as a way to reduce the influence of politicians on the courts, designed to be an independent third branch of government. Missouri's committee consisted of citizens, politicians and lawyers – principally members of the state's Republican Party – including Rush Limbaugh Sr., a prominent Cape Girardeau attorney and former legislator whose son, grandson and great grandson would go on to serve as judges. 

The legislature failed to put a nonpartisan selection system on the ballot through the referendum process, so the committee collected sufficient signatures throughout the state to put the Missouri Nonpartisan Court Plan on the ballot by initiative petition. Incorporated into the plan were fundamentals ensuring judges would be appointed on their merit and, once selected, be assured freedom from political influence and threat and freedom from conducting campaigns so they could devote themselves full-time to the work of being a judge.

Voters approved the amendment at the November 1940 general election,  but within 60 days, the legislature passed a resolution to repeal the plan during the 1942 general election. But Missouri’s voters overwhelmingly rejected the amendment, voting more strongly in favor of the nonpartisan plan than they had when they initially adopted it in 1940. The nonpartisan plan was included by the state constitutional convention that submitted the state's most recent constitution, adopted in 1945, which set the terms of Supreme Court and appeals court judges back to 12 years, the terms of circuit judges at six years and the terms of associate circuit judges at four years.

As adopted, the nonpartisan plan applied to judges of the Supreme Court; the court of appeals; the circuit, criminal corrections and probate courts of St. Louis city; and the circuit and probate courts of Jackson County. But the plan permitted local voters in any other county to determine whether they wanted their local judges to be selected using the nonpartisan plan. Based on subsequent local votes, the plan now applies in six of the state's circuit courts.

Under the Missouri Nonpartisan Court Plan, a nonpartisan judicial commission reviews applications, interviews candidates and selects a judicial panel. For the Supreme Court of Missouri and Missouri Court of Appeals, the Appellate Judicial Commission makes the selection. It is composed of three lawyers elected by the lawyers of The Missouri Bar (the organization of all lawyers licensed in this state), three citizens selected by the governor, and the chief justice,  who serves as chair. The commission includes one lawyer and one lay member from each of the geographic districts of the appeals court.

When a vacancy occurs, the commission seeks applicants and encourages the public to nominate well-qualified candidates for consideration. The commission reviews the applications of lawyers who wish to join the court and selects which applicants it will interview, then conducts those interviews in public. The commission then deliberates in a closed meeting to select a panel of three nominees for the governor's consideration. It also makes public the names and applications of the three nominees.

Initially, the constitution did not give the governor a deadline for making an appointment from among the nominees. But after a yearslong period in the 1950s during which the governor failed to appoint any nominee to fill three judicial vacancies in Jackson County, the constitution was amended to limit the governor's consideration period. Now, if the governor does not appoint one of the three nominees within 60 days of submission, the constitution requires the commission to select one of the three nominees to fill the vacancy. Since this amendment, no governor has failed to make a judicial appointment under the nonpartisan court plan.

Since its inception, the nonpartisan plan has given voters a chance to have a say in the retention of judges selected under the plan. Once a judge has served in office for at least one year, that judge must stand for a retention election at the next general election at which voters decide whether to retain the judge based on his or her judicial record. A judicial performance evaluation committee comprised of lawyers and non-lawyers evaluates judges facing retention and determine the extent to which a judge meets performance criteria. A judge must receive a majority of votes to be retained for a full term of office. To earn a subsequent full term, a judge must again win retention. If a judge retires or resigns during or at the end of his or her term, a vacancy is created, which will be filled under the Missouri Nonpartisan Court Plan as described above. The Missouri Courts website includes information about any pending nonpartisan judicial vacancies, the Appellate Judicial Commission and circuit judicial commissions, and the nonpartisan court plan.