Rebar required for 24 ft tall 4x4 square steel tube 1/4 inch thickness, 4ft deep in a concrete base, horizontal load of up to 1,000 lbs at the top
Whether your concrete base will survive is irrelevant, because your beam will fail.

See: https://www.amesweb.info/StructuralAnalysisBeams/Stresses_Steel_Hollow_Structural_Sections.aspx

Input: 
Output: 

Notice the highlighted field of the output.  That's the stress you'll be putting on the connection with the ground, (assuming it's rigid).   The yield strength of steel (where it stops bending back when unloaded) is 36,300 psi,   You'd be overloading this beam 1.5 times.  It will fail.

Consult an engineer to design something for your purposes.  

EDIT:  I've done a recalc with a cantilevered beam calculator in response to the comments below.  The result is essentially identical, and any difference between the two calculations is likely rounding. Simply put, two different calculators, with two different sets of input, give the same result:

I = 8.82813 in^4, and the 2 inches is the distance from the edge to the center.



There are two things to note in the results:


A stress of > 36000 psi, the yield strength of steel, and
A deflection at the end of almost 18 inches, which throws the geometry completely out of whack, and accelerates failure.


Further EDIT:
The Plastic Modulus for this section is 5.28 in^4
Multiply that by the yield strength gives a Plastic moment of 190,000 in.lbf, which is ~16000 ft.lbf, which is LESS than the moment at the support of 20000 ft.lbf.

TLDR: You're loading the entire structure into the plastic region, turning it into a plastic hinge.  This WILL fail.