The east side of Monterey Square is dominated by a series of one- and two-story brick storefronts, many marked with inscribed cornerstones naming and dating the buildings and identifying the architect as Jules Leffland of Victoria. This row of buildings exemplifies Leffland's impact on the urban development of small towns in the Texas Coastal Bend around the turn of the twentieth century. As can be seen from the former Leder Building and the two adjoining it to the north, Leffland used a tripartite formula to subdivide the street front, enriching the bay divisions with ornamental brick detail and varying the decorative treatment of the parapet. As simple as these differences are, they establish a repeating order that flexibly incorporates variations to avoid monotony.

Anchoring the northeast corner of Monterey Square at 101 E. Milam Street is the former Security Bank and Trust Company (now the First National Bank of El Campo), a late-nineteenth-century commercial building toned down with a neoclassical remodeling in 1928. Behind it at 112 N. Fulton Street is the former Security Bank and Trust Company (1964) by Wilson, Morris, Crain and Anderson of Houston, an exposition of precast-concrete T-roof deck construction that is now the Wharton City Hall. At the square's southeast corner the Wharton County Jail (1938) is by Houston architects Hedrick and Lindsley. Behind this building, in the 200 block of S. Fulton Street, is the 1889 county jail by Eugene T. Heiner, which still retains its modifications of 1935.