Which was the first DNA-based genome to be sequenced?
Expanding the question to the history of the sequencing of genes and genomes in general, I present a timeline taken from a review by Giani et al., entitled “Long walk to genomics: History and current approaches to genome sequencing and assembly”.

The graphic shows how the size of sequenced genes and genomes has increased since 1965, which reflects developments in sequencing technology that are discussed in this and other articles which may be more accessible. It should be noted that the more modern methodologies are not intrinsically more accurate than earlier ones, but can be employed more rapidly.
I see no value in the “Guinness Book of Records” approach to biology, but to satisfy the poster, the genome of bacteriophage φX174 was the first DNA genome to be sequenced (1977), and that of H.influenzae the first bacterial genome to be sequenced (1995). But the RNA genome of my old friend bacteriophage MS2, was the first genome to be sequenced (1976).
And the first human chromosome to be completely sequenced is not on the graphic as it was only published in Nature a few weeks ago (July 2020) — chromosome X.

Postscript
For the record, the quotation from the whole genome sequencing article is actually a caption for a (gratuitous) image of the bacterium, is unqualified, and, thus, is incorrect. But when reading Wikipedia articles it should be born in mind that they are written by people like you and me. Anyone can edit them, and nobody need check them or correct them. Peer-reviewed papers can also have mistakes, but where they are of this type, the referees should pick them up. (But by the time you read this I will have edited the Wikipedia article.)