Modifies provisions governing city-county library boards of trustees in St. Charles County

HB 2161 modifies Missouri law to establish a process for cities and counties with similar library tax levies to merge their library services into a single city-county library board. It specifically affects St. Charles County libraries (and any qualifying county under 250,000 population) by requiring the city and county to petition their respective governing bodies for approval. The bill creates a 9-member board appointed based on population comparisons: county leaders appoint more members if the county is larger, while the city mayor appoints more if the city is larger (with specific rules for counties over 400,000 population starting in 2027). It also mandates that merged libraries transfer all unspent funds and assets to the new board upon approval.