Cellulose nanocrystals (CNCs) have long been an interest of researchers because of their exceptional mechanical properties as well as being sourced from natural, inexpensive, and renewable materials. In this work, maize CNCs (m-CNC) were obtained from maize (Zea mays) husk, which is an agricultural residue. This material is a common waste product from agricultural production in different parts of the world, and of potential value if CNCs with advantageous properties are extracted from them. Maize husk is a major agricultural waste in the United States and is used for erosion prevention or to produce insulating materials, paper, and other chemicals. Dried materials were alkali treated, bleached, and hydrolyzed to CNCs using sulfuric acid. The extracted CNCs were found to have a length of 940 ± 70 nm and width of 6 ± 2 nm, high aspect ratio of approximately 157, and increase the Young’s modulus of natural rubber composites from 0.89 ± 0.15 MPa to 1.98 ± 0.73 MPa with the addition of 2 wt% m-CNCs. Other characterization techniques employed in this study are dynamic light scattering (DLS), conductometry, thermal gravimetric analysis (TGA), x-ray diffraction (XRD), and optical transmittance. Maize husks provided high aspect ratio cellulose Iβ CNCs, similar to tunicate CNCs, but with much lower processing required. Therefore, m-CNCs are more cost effective as shown by an economic evaluation. This study could provide assistance for producing CNC from one of the world’s largest supply of agricultural waste.