All 10 Uses of

sober
in
The Witch of Blackbird Pond

But the majority were soberly and poorly clad, and here and there, in the farthermost pews, Kit glimpsed the familiar black faces that must be slaves.
p. 53.7

soberly = plainly and respectably (without decoration)

"'tis not quite fair, really," Mercy considered soberly, "to hold it against Kit, just because we thought—"
p. 67.1

soberly = in a serious manner

Sober little adults they had appeared on that first day, dressed in fashions much like their parents'.
p. 84.8

sober = serious-minded

...and then she was laughing with Hannah. But instantly she sobered again.
p. 96.6 *

sobered = became serious

The sober young divinity student seemed an odd match for Judith's high spirits.
p. 102.1

sober = serious-minded

Watching Mercy this morning, she thought again, soberly, of the words that Mercy had spoken earlier in the summer.
p. 111.5

soberly = in a serious manner

Kit could have laughed out loud, but a look at Goodwife Cruff sobered her.
p. 198.9

sobered = made serious

No one paid attention to the two tardy guests who appeared at the door, letting in a gust of wind, till suddenly a woman screamed and threw her arms about a snow-covered figure. Then abruptly the music stopped and the laughter was checked, and everyone crowded about the newcomers. ... The story they had to tell put a somber end to the happy evening. ... The sobered guests crowded close, waiting for one answer.
p. 233.5

Definitions:

(1) (sober as in: Talk to me when your sober.)
not under the influence of alcohol
(2) (sober up as in: I need to sober up.)
to become less drunk or intoxicated
(3) (sobering as in: a sobering thought)
serious or calm (not silly or excited); or making one serious or less excited
(4) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely, sober can refer to one who is rational rather than under the influence of extreme emotion. Also more rarely, it can reference that which is practical rather than fanciful -- such as "a more sober plan."