From 358432b5d58480650f980a1453ce0a680c202b7d Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Thu, 31 Aug 2023 23:41:12 +0200
Subject: [PATCH 1/2] REGR: concat raising for 2 different ea dtypes

---
 doc/source/whatsnew/v2.1.1.rst             | 1 +
 pandas/core/internals/concat.py            | 2 +-
 pandas/tests/reshape/concat/test_concat.py | 9 +++++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.1.1.rst b/doc/source/whatsnew/v2.1.1.rst
index f5aa0968ae362..1452418e2abe9 100644
--- a/doc/source/whatsnew/v2.1.1.rst
+++ b/doc/source/whatsnew/v2.1.1.rst
@@ -13,6 +13,7 @@ including other versions of pandas.
 
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
+- Fixed regression in :func:`concat` when :class:`DataFrame`'s have two different extension dtypes (:issue:`54848`)
 - Fixed regression in :meth:`DataFrame.__setitem__` raising ``AssertionError`` when setting a :class:`Series` with a partial :class:`MultiIndex` (:issue:`54875`)
 
 .. ---------------------------------------------------------------------------
diff --git a/pandas/core/internals/concat.py b/pandas/core/internals/concat.py
index 4d33f0137d3c4..b2d463a8c6c26 100644
--- a/pandas/core/internals/concat.py
+++ b/pandas/core/internals/concat.py
@@ -177,7 +177,7 @@ def concatenate_managers(
                 values = np.concatenate(vals, axis=1)  # type: ignore[arg-type]
             elif is_1d_only_ea_dtype(blk.dtype):
                 # TODO(EA2D): special-casing not needed with 2D EAs
-                values = concat_compat(vals, axis=1, ea_compat_axis=True)
+                values = concat_compat(vals, axis=0, ea_compat_axis=True)
                 values = ensure_block_shape(values, ndim=2)
             else:
                 values = concat_compat(vals, axis=1)
diff --git a/pandas/tests/reshape/concat/test_concat.py b/pandas/tests/reshape/concat/test_concat.py
index 3efcd930af581..5dde863f246d1 100644
--- a/pandas/tests/reshape/concat/test_concat.py
+++ b/pandas/tests/reshape/concat/test_concat.py
@@ -858,3 +858,12 @@ def test_concat_multiindex_with_category():
     )
     expected = expected.set_index(["c1", "c2"])
     tm.assert_frame_equal(result, expected)
+
+
+def test_concat_ea_upcast():
+    # GH#54848
+    df1 = DataFrame(["a"], dtype="string")
+    df2 = DataFrame([1], dtype="Int64")
+    result = concat([df1, df2])
+    expected = DataFrame(["a", 1], index=[0, 0])
+    tm.assert_frame_equal(result, expected)

From 4238e6dd107ff732c623d02a4c760d4fd872e744 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Fri, 1 Sep 2023 13:26:27 +0200
Subject: [PATCH 2/2] Update

---
 doc/source/whatsnew/v2.1.1.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.1.1.rst b/doc/source/whatsnew/v2.1.1.rst
index 2699bb58b0645..b677a341798e0 100644
--- a/doc/source/whatsnew/v2.1.1.rst
+++ b/doc/source/whatsnew/v2.1.1.rst
@@ -13,7 +13,7 @@ including other versions of pandas.
 
 Fixed regressions
 ~~~~~~~~~~~~~~~~~
-- Fixed regression in :func:`concat` when :class:`DataFrame`'s have two different extension dtypes (:issue:`54848`)
+- Fixed regression in :func:`concat` when :class:`DataFrame` 's have two different extension dtypes (:issue:`54848`)
 - Fixed regression in :func:`read_csv` when ``usecols`` is given and ``dtypes`` is a dict for ``engine="python"`` (:issue:`54868`)
 - Fixed regression in :meth:`DataFrame.__setitem__` raising ``AssertionError`` when setting a :class:`Series` with a partial :class:`MultiIndex` (:issue:`54875`)
 - Fixed regression when comparing a :class:`Series` with ``datetime64`` dtype with ``None`` (:issue:`54870`)