Sirius Black’s mother, Walburga, is born

Lucretia Black Prewett is born

Timeline Notes
This is almost certainly not Molly Weasley's mother, as this would make Molly and Sirius cousins - not "cousins by marriage" as Sirius describes (OP6). More likely is that Ignatius Prewett, who married Lucretia, is Molly's uncle.

Phineas Nigellus Black dies

Phineas Nigellus is the least popular Headmaster Hogwarts ever had, at least according to his great-great-grandson, Sirius (OP6).

McLaird’s eccentric behavior results in his being forced out of office

Members of the Wizarding government find his penchant for monosyllables and smoke signals annoying and they force him out as Minister for Magic.

Hector Fawley becomes Minister for Magic

Fawley’s gregarious and flamboyant style is a marked contrast to the taciturn nature of his predecessor.

Notes
Fawley was Minister for Magic during the events of at least the first two films in the Fantastic Beasts series, which take place in 1926 and 1927. In the scene at MACUSA headquarters where the International Confederation of Wizards is meeting, Newt Scamander addresses someone in the crowd of dignitaries as "Minister." This may be intended to be Hector Fawley. However, the actor who played that part is listed by his agent as having played the part of "Hector Podmore." The part is listed simply as "British Envoy" on IMDb

circa September, 1925

Bob Ogden visits the Gaunt house on a routine follow-up

"'Morfin has broken Wizarding law' ... He taught a filthy Muggle a lesson, that's illegal now, is it?"
-- Marvolo Gaunt to Bob Ogden, who responded with "Yes, I'm afraid it is!" (HBP10)

Ogden is investigating an attack on a Muggle by Morfin Gaunt late the previous evening. In the yard outside the hovel, Ogden is attacked by Morfin, then he encounters the irate Marvolo Gaunt who, along with his son Morfin, refuse to admit Morfin has done anything wrong, either in attacking the Muggle or in attacking Ogden. When Bob Ogden steps in to stop them injuring Morfin’s sister, Merope, he is driven from the house (HBP10).

Timeline Notes
This happens "a few months" before Merope marries Tom Riddle.

Morfin Gaunt attacks Tom Riddle Sr. with hives jinx

"But I got him, Father. I got him as he went by, and he didn’t look so pretty with hives all over him, did he Merope?"
-- Morfin Gaunt, speaking in Parseltongue (HBP10)

Merope Gaunt liked to wait by the window for a glimpse of handsome Tom Riddle Sr., a rich Muggle boy. Morfin Gaunt, Merope’s brother, mocked her for it and late one night he caught her at it. Just for spite, he hit Tom Riddle Sr. with a Hives Jinx. This attack brought a visit from Bob Ogden, Head of the Department for Magical Law Enforcement, the next day (HBP10).

Timeline Notes
Since Mofin was summoned to appear on September 14th, these events must have happened in early September. The year would be 1925, the year before Merope used a love potion to force Tom Riddle Sr. to marry her and father a child, who was born on December 31, 1926.

Bob Ogden returns to the Gaunt home with reinforcements, Marvolo and Morfin are arrested

Fifteen minutes after fleeing from Morfin Gaunt’s attack on him (for physically restraining Morfin from attacking Merope) and apparating back to the Ministry of Magic, Bob Ogden returns to the Gaunt cottage – this time with reinforcements who succeeded in overpowering the Gaunt men, although several are injured by Marvolo.

After the arrests, the Wizengamot sentences Morfin to three years in Azkaban and his father, Marvolo, to six months in Azkaban.

circa December, 1925

Merope Gaunt fools Tom Riddle into marrying her

c. December 1925 – Merope Gaunt, besotted as she is with the handsome Muggle who rides his horse near her miserable hovel, somehow hoodwinks him into marrying her. Most likely, she does so by giving him a love potion.

Timeline Notes
Dumbledore says that Merope and Riddle were married about a year before Tom Marvolo Riddle was born, which was on December 31, 1926.