Compositions and methods for obtaining plant cells with modified Ht1 nucleotide sequences, modified NLB18 sequences, or both, are provided herein. The methods involve introducing double-strand breaks into the maize genome in an endogenous Ht1 encoding sequence, an endogenous NLB18 encoding sequence, or both, to modify the genomic sequence in order to enhance northern leaf blight resistance of a plant produced from the plant cell. Further provided are methods that introduce resistance alleles of Ht1 and/or NLB18 into specific sites in the genome. Plants produced by the plant cells, and seeds produced from the plants are also included. Guide polynucleotides are also provided for the use of the CRISPR-Cas system in inducing double strand breaks.