Insofar as Texas is concerned (and all states admitted after 1796,
Tennessee inclusive), the question is resolved in the enabling
legislation by which the state was admitted: all states are admitted
on an equal footing with the original states.
Joint Resolution for Annexing Texas to the United States
"3. And be it further resolved, That if the President of the United
States shall in his judgment and discretion deem it most advisable,
instead of proceeding to submit the foregoing resolution of the
Republic of Texas, as an overture on the part of the United States for
admission, to negotiate with the Republic; then, Be it resolved, That
a State, to be formed out of the present Republic of Texas, with
suitable extent and boundaries, and with two representatives in
Congress, until the next appointment of representation, shall be
admitted into the Union, by virtue of this act, on an equal footing
with the existing States, as soon as the terms and conditions of such
admission, and the cession of the remaining Texian territory to the
United States shall be agreed upon by the governments of Texas and the
Approved, March 1, 1845."
When a state is admitted to the Union, it is as if that new state had
always been in the Union from the beginning. There is no distinction
between new and original states: all enjoy the same status. Thus, the
citizens of the new state enjoy the same privileges and rights as
their fellows in the other states, as if they had always possessed
Equal Footing - state constitutions
'As stated by Justice Field in Escanaba & Lake Michigan Transp. Co. v.
City of Chicago, 107 U.S. 678 (1883):
"...although the act of April 18, 1818, enabling the people of
Illinois territory to form a constitution and state government, and
the act of August 26th, following, admitting the state into the Union,
refer to the principles of the [Northwest] ordinance according to
which the constitution was to be formed,-its provisions could not
control the authority and powers of the state after her admission.
Whatever the limitation upon her powers as a government while in a
territorial condition, whether from the ordinance of 1787 or the
legislation of congress, it ceased to have any operative force, except
as voluntarily adopted by her after she became a state of the Union.
On her admission she at once became entitled to and possessed of all
the rights of dominion and sovereignty which belonged to the original
states. She was admitted, and could be admitted, only on the same
footing with them. The language of the act of admission is, 'on an
equal footing with the original states in all respects whatever.' 3
St. 536. Equality of constitutional right and power is the condition
of all the states of the Union, old and new...."'