Shonkin Sag
... that Montana's Shonkin Sag was created when glaciers blocked the Missouri River, forcing it to cut a new channel at right angles to the existing drainage valleys?
... that <a href="./Montana" id="mwDg8" rel="mw:WikiLink" title="Montana">Montana</a>'s <b id="mwDhA"><a href="./Shonkin_Sag" id="mwDhE" rel="mw:WikiLink" title="Shonkin Sag">Shonkin Sag</a></b> was created when <a class="mw-redirect" href="./Last_glacial_period" id="mwDhI" rel="mw:WikiLink" title="Last glacial period">glaciers</a> blocked the <a href="./Missouri_River" id="mwDhM" rel="mw:WikiLink" title="Missouri River">Missouri River</a>, forcing it to cut a new channel at right angles to the existing drainage valleys?