The Shulhan Arukh on How Much Time to Wait to Eat Dairy After Consuming Meat

In honor of finishing my milk & meat test (בחינה של בשר בחלב), I decided to quote and translate section 89:1 of the Shulhan Arukh (Yoreh Deah), the mid-16th century Jewish law work, on how much time one is to wait between eating meat and milk. Up first is Rabbi Yosef Karo:

אכל בשר, אפילו של חיה ועוף, לא יאכל גבינה אחריו עד שישהה שש שעות. ואפילו אם שהה כשיעור, אם יש בשר בין השינים, צריך להסירו.
והלועס לתינוק, צריך להמתין.

If one ate meat - even a wild beast or poultry - one should not eat cheese after that until one waits six hours. And even if one waited that amount of time, if there is still flesh/meat in one's teeth, one needs to remove it.
And one who chews up [meat] for a child/toddler needs to wait [the prescribed amount of time].

However, Rabbi Moshe Isserles wrote

ואם מצא אחר כך בשר שבין השינים, ומסירו, צריך להדיח פיו קודם שיאכל גבינה (הר"ן פכ"ה). ויש אומרים דאין צריכין להמתין שש שעות, רק מיד אם סלק ובירך ברכת המזון, מותר על ידי קנוח והדחה (תוס' ומרדכי פכ"ה והגהות אשיר"י והג"ה מיימוני פ"ט דמ"א וראבי"ה).
והמנהג הפשוט במדינות אלו, להמתין אחר אכילת הבשר שעה אחת, ואוכלין אחר כך גבינה. מיהו צריכים לברך גם כן ברכת המזון אחר הבשר (ע"פ הארוך והגהות ש"ד), דאז הוי כסעודה אחרת, דמותר לאכול לדברי המקילין. אבל בלא ברכת המזון, לא מהני המתנת שעה. ואין חילוק אם המתין השעה קודם ברכת המזון, או אחר כך (ד"ע ממהרא"י ולאפוקי או"ה). ואם מצא בשר בין שיניו, אחר השעה, צריך לנקרו ולהסירו (ד"ע ממשמעות הר"ן הנ"ל).
ויש אומרים דאין לברך ברכת המזון על מנת לאכול גבינה (ארוך בשם מהר"ח), אבל אין נזהרין בזה.
ויש מדקדקים להמתין שש שעות אחר אכילת בשר לגבינה, וכן נכון לעשות

If one found meat between ones teeth afterwards and removes it, one needs to wash out one's mouth prior to eating cheese.
There are those who say that one does not need to wait six hours, but, rather just to remove their plate and to bless the Grace After Meals and it is permitted through wiping and rinsing.
The simple custom in these lands is to wait one hour after eating meat, and then [to be able] to eat cheese. However, one still needs to bless the Grace After Meals after the meat, because it would be like another meal, for which it would be permissible to eat, according to those who are lenient. But without the Grace After Meals, waiting an hour does not help. And there is no difference if one waits an hour before the Grace After Meals or afterwards. If one found meat between one’s teeth after that hour, one needs to remove it.
Some say one should not say the Grace After Meals just to eat cheese, but we are not concerned about this.
There are some who are meticulous to wait six hours after eating meat before [eating] cheese. And such is proper to do.

For Rabbi Isserles' use of the term "these lands", I will refer to Joseph Davis' excellent article:

"These lands" is a phrase that Isserles was fond of, and he used it several times in his Responsa. In one place, he contrasted "these lands" to Italy.... In another place, he contrasted "these lands" to Moravia.... In a third responsum..., Isserles contrasted "these lands" to Germany....
Isserles used "these lands" to mean the lands of Poland. The "customs of these lands" that Isserles codified in his notes to the Shulhan Arukh were the customs of the Polish Jews.

-Joseph Davis, "The Reception of the Shulhan Arukh and the Formation of Ashkenazic Jewish Identity," AJS Review 26, no. 2 (2002), 265.
For more on this topic, my havrusa wrote a little piece on this same topic (you have to scroll down a little).