If a solution was possible to tile a 70x70 square with squares $$1^2+2^2+\cdots+24^2$$ then a perfect squared square of order 24 would exist.  Order 24 has been completely enumerated.  The compound perfect squared squares (CPSSs - compound; subrectangles allowed) of order 24 were generated by Duijvestijn, Federico and Leeuw in 1979 and 1982.  Only 1 CPSS of order 24 was found, T.H. Willcocks 175x175, discovered in 1948.
The 26 simple perfect squared squares (SPSSs - simple; no subrectangles allowed) of order 24 were enumerated by Duijvestijn in 1991, the smallest SPSS of that order being 120x120.  These results have been confirmed a number of times by other researchers using different approaches and software.

The sum of squares formula gives;$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$$

$$For\ n = 32,\ i^2 = 11440, \sqrt{11440}= 106.95794..$$
$$For\ n = 33,\ i^2 = 12529, \sqrt{12529}= 111.93301..$$
If perfect squared squares existed with a side less than 110 in length then they would need to be of order 32 or less (if the 33 squares from 1 to 33^2 will not fit in a square of side 110, neither will a larger set of 33 squares, nor will any order higher than 33).  All orders of perfect squares squares up to and including order 33, both simple and compound, have been enumerated, see <a href="www.squaring.net">squaring.net</a>.  The smallest perfect squared squares found up to order 33 were the 3 SPSSs with sides of 110.  There are 2 in order 22, and 1 in order 23.  So these are the smallest possible perfect squared squares .  Note that the 112 side SPSS found by Duijvestijn in 1978 is the lowest order (21) perfect squared square, but not the smallest.

Gambini achieved the same result, that 110 is the smallest perfect squared square in his 1999 thesis, using a packing program.