diff --git a/oxrlib/config.py b/oxrlib/config.py
index cdb757462aad75988b1925a20013c84d6a3631b6..4c4877d5aa411e8b271feb27a4d59454c81b14f8 100644
--- a/oxrlib/config.py
+++ b/oxrlib/config.py
@@ -5,6 +5,9 @@ import decimal
 import os.path
 import pathlib
 
+import babel
+import babel.numbers
+
 from . import cache, loaders
 
 HOME_PATH = pathlib.Path(os.path.expanduser('~'))
@@ -20,7 +23,8 @@ def currency_list(s):
 class Configuration:
     DATE_SEPS = frozenset('.-/ ')
     DEFAULT_CONFIG_PATH = pathlib.Path(HOME_PATH, '.config', 'oxrlib.ini')
-    NO_DENOMINATION = object()
+    LOCALE = babel.core.Locale.default()
+    SENTINEL = object()
     PREPOSITIONS = frozenset(['in', 'to', 'into'])
     TODAY = datetime.date.today()
 
@@ -106,7 +110,7 @@ class Configuration:
         )
         hist_parser.add_argument(
             '--no-denomination',
-            dest='denomination', action='store_const', const=self.NO_DENOMINATION,
+            dest='denomination', action='store_const', const=self.SENTINEL,
             help="Turn off an earlier --denomination setting",
         )
         hist_parser.add_argument(
@@ -134,7 +138,7 @@ class Configuration:
         hist_parser.add_argument(
             'word3', nargs='?', metavar='second code',
             help="Convert or show rates to this currency, in three-letter code format. "
-            "If not specified, defaults to the base currency.",
+            "If not specified, defaults to the user's preferred currency.",
         )
         hist_parser.add_argument('word4', nargs='?', help=argparse.SUPPRESS)
 
@@ -170,20 +174,27 @@ class Configuration:
             errmsg.append(repr(s_value))
             self.error(': '.join(errmsg))
 
+    def _user_currency(self, default=SENTINEL):
+        try:
+            return babel.numbers.get_territory_currencies(
+                self.LOCALE.territory, start_date=self.TODAY)[0]
+        except IndexError:
+            return default
+
     def _post_hook_historical(self):
         year = self.args.date.year
         if year < 100:
             # Don't let the user specify ambiguous dates.
             self.error("historical data not available from year {}".format(year))
         self._read_from_conffile('base', 'Historical', 'USD', currency_code)
-        if self.args.denomination is self.NO_DENOMINATION:
+        if self.args.denomination is self.SENTINEL:
             self.args.denomination = None
         else:
             self._read_from_conffile('denomination', 'Historical', None, currency_code)
-        self._read_from_conffile('signed_currencies', 'Historical', self.args.base,
+        pref_currency = self.args.denomination or self._user_currency(self.args.base)
+        self._read_from_conffile('signed_currencies', 'Historical', pref_currency,
                                  currency_list, convert_fallback=True)
         self._read_from_conffile('ledger', 'Historical', False, getter='getboolean')
-        self.args.to_currency = self.args.base
         raw_words = iter(getattr(self.args, 'word' + c) for c in '1234')
         words = iter(word for word in raw_words if word is not None)
         try:
@@ -202,7 +213,7 @@ class Configuration:
                 next_word = next(words, next_word)
             self.args.to_currency = self._convert_or_error(currency_code, next_word)
         except StopIteration:
-            pass
+            self.args.to_currency = pref_currency
 
     def _build_cache_loader(self):
         kwargs = dict(self.conffile.items('Cache'))