diff --git a/src/Nonemm.Session/OperatingPosition.cs b/src/Nonemm.Session/OperatingPosition.cs
index 8239a63..f78d705 100644
--- a/src/Nonemm.Session/OperatingPosition.cs
+++ b/src/Nonemm.Session/OperatingPosition.cs
@@ -341,20 +341,24 @@ public sealed class OperatingPosition
         return filled;
     }
 
-    /// Fills what the call history knows into the exchange boxes that are still
-    /// empty. What the other station actually sends wins, so a box with
-    /// something in it is left alone. Returns true when anything was filled.
+    /// Fills what is already known about the station into the exchange boxes
+    /// that are still empty. What the other station actually sends wins, so a
+    /// box with something in it is left alone. A zone box takes the call
+    /// history file first, then the zone logged on the last contact with the
+    /// call, then the zone the country file gives for the callsign, which is
+    /// what N1MM does. Returns true when anything was filled.
     public bool FillFromHistory()
     {
         CallHistoryEntry? known = Session.History.Find(Entry.Call);
-        if (known is null)
-        {
-            return false;
-        }
         bool filled = false;
         for (int at = 0; at < Entry.Exchange.Count; at++)
         {
-            string value = ExchangeSlots.ValueFrom(known, Entry.Exchange[at]);
+            ExchangeField field = Entry.Exchange[at];
+            string value = known is null ? "" : ExchangeSlots.ValueFrom(known, field);
+            if (value.Length == 0)
+            {
+                value = KnownZone(field);
+            }
             if (value.Length == 0 || Entry[at + 1].Trim().Length > 0)
             {
                 continue;
@@ -369,6 +373,27 @@ public sealed class OperatingPosition
         return filled;
     }
 
+    /// The zone to suggest for a zone box: the one on the newest earlier
+    /// contact with this call that has one, else the country file's zone.
+    /// Empty for any other box.
+    private string KnownZone(ExchangeField field)
+    {
+        if (field.Kind is not (ExchangeFieldKind.CqZone or ExchangeFieldKind.ItuZone))
+        {
+            return "";
+        }
+        string logged = WorkedBefore()
+            .Select(qso => ExchangeSlots.ValueOf(qso, field.Slot))
+            .FirstOrDefault(value => value.Length > 0) ?? "";
+        if (logged.Length > 0)
+        {
+            return logged;
+        }
+        CountryLookup? their = Country();
+        int zone = their is null ? 0 : field.Kind == ExchangeFieldKind.CqZone ? their.CqZone : their.ItuZone;
+        return zone > 0 ? zone.ToString() : "";
+    }
+
     /// Moves to the next box the operator types in. On top of the report boxes
     /// the entry itself steps over, a contest can say a box is not for this
     /// station: CQ WW RTTY asks only the US and Canada for a state.
diff --git a/tests/Nonemm.Session.Tests/OperatingPositionTests.cs b/tests/Nonemm.Session.Tests/OperatingPositionTests.cs
index 6ffae66..0505866 100644
--- a/tests/Nonemm.Session.Tests/OperatingPositionTests.cs
+++ b/tests/Nonemm.Session.Tests/OperatingPositionTests.cs
@@ -482,6 +482,32 @@ public class OperatingPositionTests
         Assert.Equal("25", session.Entry.ValueOf(ExchangeSlot.Zone));
     }
 
+    /// N1MM suggests the country's zone when the call is settled.
+    [Fact]
+    public void TheCountryFileZoneFillsTheZoneBox()
+    {
+        OperatingPosition session = Session();
+        session.Entry.Call = "JA1XYZ";
+
+        Assert.True(session.FillFromHistory());
+        Assert.Equal("25", session.Entry.ValueOf(ExchangeSlot.Zone));
+    }
+
+    /// A zone copied on an earlier contact beats the country's own.
+    [Fact]
+    public void TheZoneLoggedBeforeBeatsTheCountryFileZone()
+    {
+        OperatingPosition session = Session();
+        Type(session, "DL1ABC", "40");
+        session.LogContact();
+        session.Wipe();
+        session.Entry.Call = "DL1ABC";
+
+        session.FillFromHistory();
+
+        Assert.Equal("40", session.Entry.ValueOf(ExchangeSlot.Zone));
+    }
+
     /// A file for a section contest often carries the state instead.
     [Fact]
     public void TheStateFillsASectionWhenTheFileHasNoSection()