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- Oaklawn on Mishawaka ground: the successor designation arrives Mental Health Institutions
- October 1973: the great wave passes the county by UFO Sightings
- The Odd Fellows: St. Joseph Lodge No. 27, Monitor Lodge No. 286, and the Rebekahs Lodges & Fraternal Orders
- The Odd Fellows: the first lodge, the fire, and Monitor Lodge No. 286 Private Clubs
- The Official Books: Acts, Charters, Minutes, the City's Own Pages Sources
- The old building after: easements, an aircraft museum that never was, and a dining room Libraries
- The Old-Settlers' Stock: Merrifield's Articles, Brunner's 137 Essays, and the Certificates Folklore
- The Oldest Possession Museums
- The oldest-institution claims, one by one — school, bank, zoo, and two papers of record correcting themselves Famous Stories & the Record
- The Olympian test — negative, printed at true size Sports
- One Biography per Artist: The Roster at Record Size Arts
- The one Bitcoin prosecution: the search, printed whole Lottery & Crypto
- One documented concert, and the famous-name test Music
- One ground, two industries: the woolen mill becomes a rubber works Industrial Revolution
- One metro, two cities The Story of Mishawaka
- One seat to Elkhart again: Route 30 and the CONNECT redesign, 2025 Public Transit
- The one that closed · Theresa Burns Cold Cases
- One town, one name: the act of 1838 The Story of Mishawaka
- The opening and the anchor course, 1979–1980 Malls & Shopping
- The orders that came after the roster: Moose and Eagles Lodges & Fraternal Orders
- The organ maker and the first church music: Van Dinter's Mishawaka Music
- Organizational Succession: The Groups Around the System Trails
- The organizations as they stand Veterans
- Organized fun at city hall: the recreation department's documented course Kids & Family Entertainment
- The Orthodox Set: A Backyard Church in Mishawaka, and the Valley's Parishes Across the Line Churches & Religion
- The other instruments: Barbee, Indiana City, the Fowlers, Taylor Land Surveys & Titles
- The other name: the Power City, and the works in the street names Culture
- The other regiments: the county's war beyond two companies Wars, Unrest & Disasters
- The other rooms of 1925: five houses the nomination counts and does not name Theaters
- The Other Shelves: HathiTrust, the Catalogs, Indiana Memory, the Paywalled Doors, First-Party Reads Sources
- "Our Team Will Fight Like Cavemen!": The Sentence's Growth, Stage by Stage Folklore
- Ownership: the LTV and Renco years AM General
- Ownership: the Perelman venture and KPS AM General