Question: When was the catastrophic EF5-rated multiple-vortex tornado struck after which the Missouri Militia members have been active in disaster relief?
Context: The Early-April 1957 tornado outbreak sequence was a deadly tornado outbreak sequence that struck most of the Southern United States from April 2–5, 1957.  The outbreak killed at least 21 people across three states and produced at least 72 tornadoes from Texas to Virginia.  The outbreak was most notable due to a tornado that hit a densely populated area of the Dallas–Fort Worth metropolitan area, killing 10 people and injuring 200 or more.  The tornado, highly visible for most of its path, was at the time the most observed and best-documented tornado in recorded history; hundreds of people photographed or filmed the F3 tornado as it moved just west of Downtown Dallas.  The film of this tornado is still known for its unusually high quality and sharpness, considering the photography techniques and technology of the 1950s.  Damage from the Dallas tornado reached as high as $4 million (1957 USD).  Besides the famous Dallas tornado, other deadly tornadoes struck portions of Mississippi, Texas, and Oklahoma.  Two F4 tornadoes struck southern Oklahoma on April 2, killing five people.  Three other significant, F2-rated tornadoes that day killed two people in Texas and one more in Oklahoma.  An F3 tornado struck rural Mississippi on April 4, killing one more person.  In addition to confirmed tornadoes, a possible tornado hit Ballard County, Kentucky, on April 3, unroofing homes, destroying a drive-in theater, and uprooting trees.  A loud roaring noise was heard.  Two other brief tornadoes may have hit near Westlake and at Tallulah, Louisiana, late on April 4. The 2011 Tuscaloosa–Birmingham tornado was a large and violent EF4 multiple-vortex tornado that devastated portions of Tuscaloosa and Birmingham, Alabama, as well as smaller communities and rural areas between the two cities, during the late afternoon and early evening of Wednesday, April 27, 2011.  It is one of the costliest tornadoes on record.  It was one of the 362 tornadoes in the 2011 Super Outbreak, the largest tornado outbreak in United States history.  The tornado reached a maximum path width of 1.5 mi during its track through Tuscaloosa, and once again when it crossed Interstate 65 north of Birmingham, and attained estimated winds of 190 mph shortly after passing through the city.  It then went on to impact parts of Birmingham as a high-end EF4 before dissipating.  This was the third tornado to strike the city of Tuscaloosa in the past decade, and the second in two weeks. Public Law 113-2 (Pub.L.  113–2 , , 127 Stat.  4 , enacted  29, 2013 ), containing Division A: Disaster Relief Appropriations Act, 2013 and Division B: Sandy Recovery Improvement Act of 2013 is a U.S. appropriations bill authorizing $60 billion for disaster relief agencies.  The Budget Control Act of 2011 (BCA), had authorized only disaster spending and emergency spending to exceed established spending caps.  While emergency spending is not subject to the caps in the BCA, spending for disaster relief is calculated by taking the average of the previous ten years disaster relief spending, excluding the highest and lowest spending years. The Windsor Locks, Connecticut tornado struck the towns of Windsor, Windsor Locks, and Suffield, Connecticut and Feeding Hills, Massachusetts on October 3, 1979.  The short-lived but intense tornado struck without warning and caused three deaths and 500 injuries. The Missouri Militia is a private, non-profit civilian defense organization in the U.S. state of Missouri.  The Missouri Militia is not a part of the Missouri Reserve Force.  which is the state defense force for the state of Missouri.  Its members have been active in disaster relief after the 2011 Joplin tornado. The 1948 Tinker Air Force Base tornadoes were two tornadoes which struck Tinker Air Force Base in Oklahoma City, Oklahoma, on March 20 and 25, 1948.  Both are estimated to have been equivalent to F3 in intensity on the modern Fujita scale of tornado intensity, which was not devised until 1971.  The March 20 tornado was the costliest tornado in Oklahoma history at the time.  On March 25, meteorologists at the base noticed the extreme similarity between the weather conditions of that day and March 20, and later in the day issued a "tornado forecast", which was verified when a tornado struck the base that evening.  This was the first official tornado forecast, as well as the first successful tornado forecast, in recorded history. The Provisional Enrolled Missouri Militia or PEMM also known as the Detailed Militia was a state militia organization of Missouri's Union government during the American Civil War.  Unlike the Enrolled Missouri Militia it was a full-time force. A multiple-vortex tornado is a tornado that contains several vortices (called subvortices or suction vortices) rotating around, "inside" of, and as part of the main vortex.  The only times multiple vortices may be visible are when the tornado is first forming or when condensation and debris is balanced enough so that subvortices are apparent without being obscured.  They can add over 100 mph to the ground-relative wind in a tornado circulation, and are responsible for most (if not all) cases where narrow arcs of extreme destruction lie right next to weak damage within tornado paths. The June 1974 Great Plains tornado outbreak was a significant tornado outbreak that affected portions of the southern Great Plains and the Upper Midwest on June 8, 1974.  The outbreak produced 36 tornadoes, at least 19 of them significant or intense, and is the second-deadliest June tornado event in Oklahoma history, with 16 deaths reported in the state, second only to the 35 people killed by an F4 tornado on June 12, 1942, in Oklahoma City.  The deadliest tornado of the outbreak was a powerful F4 that struck the town of Drumright in Oklahoma, killing 14 people, 12 of whom were killed at Drumright.  Another deadly and destructive F4 tornado struck the town of Emporia in Kansas, killing six more people.  The outbreak also produced two F3 tornadoes in the Tulsa metropolitan area that killed two people and, combined with flooding, produced the costliest natural disaster in that city's history up to that time—a disaster worth $30,000,000 (1974 USD).  Additionally, the outbreak produced non-tornadic winds in the city which reached 100 kn (115 mi/h ) for several minutes.  In addition to confirmed tornadoes, a possible tornado occurred at 8:15 p.m. CST 5 mi south of Cullison in Kansas, producing intermittent damage, but is not officially listed as a tornado. The 2011 Joplin tornado was a catastrophic EF5-rated multiple-vortex tornado that struck Joplin, Missouri, late in the afternoon of Sunday, May 22, 2011.  It was part of a larger late-May tornado outbreak and reached a maximum width of nearly 1 mi during its path through the southern part of the city.  It rapidly intensified and tracked eastward across the city, and then continued eastward across Interstate 44 into rural portions of Jasper County and Newton County.  It was the third tornado to strike Joplin since May 1971.
Answer: May 22, 2011