An approximate answer
It is exceedingly rare, if it has ever happened, for a lawyer with less than three years of experience whose only courtroom experience is serving as third chair lawyer in a hearing to be appointed as a U.S. District Court judge.
Overwhelmingly, these federal trial court judges are only appointed after they have considerable experience as lawyers and made a reputation for themselves as trial court litigators (most often as prosecuting attorneys).
Lawyers with little trial court experience, such as lawyers whose primary experience is as an appellate litigator or as an academic are sometimes appointed to serve as appellate judges where familiarity with trial practice is not at as much of a premium. But, it would still be unheard of to appoint a lawyer with less than three years of experience to an appellate court.
While I won't say that this has "never" happened, if it has ever happened, you can probably count the number of cases on your fingers.
Location of source data
A complete data set is available in the Federal Judicial Center's Biographical Directory of Article III Judges. A list of all federal judges who were nominated but not confirmed can be found here. There were 352 federal judges who ultimately took office who were nominated prior to January 1, 1888 (roughly speaking before intermediate appellate courts were established). There are 3,241 federal judges who ultimately took office who were nominated after that date.
I don't have the capacity to do a full analysis of that data and have not been able to locate an analysis of this data in the literature although I am sure that there is one somewhere.
One can judge how unusual or not this practice is, in the absence of a full analysis of the entire data set, by considering statutory and bar association norms regarding legal experience for judges.
Bankruptcy judges are required to have five years of experience as a lawyer, but no similar requirements exists for other Article III judges. State court magistrates in Colorado are required to have five years of experience as practicing lawyers (most have more) as do most other judgeships (like some other states part-time limited jurisdiction court judges in a few rural counties are not required to be lawyers in Colorado, about four are not, but every state requires judges in general jurisdiction courts to be lawyers and this is also an almost universal norm in the federal judicial system).
The American Bar Association benchmark for serving as a federal judge in evaluations it has done of every federal judicial nominee since 1953 has been to expect 12 years of experience as a lawyer. The ABA Standard on Professional Experience reads as follows:
A candidate should be a licensed, experienced lawyer.
A candidate should be admitted to practice law in the jurisdiction.
The length of time that a lawyer has practiced is a valid criterion in
screening candidates for judgeships. Such professional experience
should be long enough to provide a basis for the evaluation of the
candidate's demonstrated performance and long enough to ensure that
the candidate has had substantial exposure to legal problems and the
It is desirable for a candidate to have had substantial trial
experience. This is particularly true for a candidate for the trial
bench. Trial experience includes the preparation and presentation of
matters of proof and legal argument in an adversary setting. The
extent and variety of an candidate's experience as a litigator should
be considered in light of the nature of the judicial vacancy that is
being filled. Although substantial trial experience is desirable,
other types of legal experience should also be carefully considered.
An analysis of the work performed by the modern trial bench indicates
that, in addition to adjudication, many judges perform substantial
duties involving administration, discovery, mediation and public
relations. A private practitioner who has developed a large clientele,
a successful law teach and writer or a successful corporate,
government or public interest attorney all may have experience which
will contribute to successful judicial performance. Outstanding
persons with such experience should not be deemed unqualified solely
because of lack of trial experience. The important consideration is
the depth and breadth of the professional experience and the
competence with which it has been performed, rather than the
candidate's particular type of professional experience.
For a candidate for the appellate bench, professional experience
involving scholarly research and the development and expression of
legal concepts is especially desirable.
Violations of the ABA norms in the nomination process in modern history is very uncommon. This letter in opposition notes that:
[T]he ABA panel evaluating Talley’s nomination has unanimously agreed
that he is not qualified to be a federal judge. It is hardly common
for a judicial nominee to be deemed unqualified by a majority of the
ABA panel. But unanimous agreement on such a devastating evaluation is
exceedingly rare. In the 28 years of nominee evaluations on the ABA’s
website, this is only the fourth time. (The third time was just a
couple of weeks ago, with another Trump nominee.)
The other three candidates unanimously deemed unqualified by the ABA Committee all had more experience than Talley. The other Trump nominee unanimously rated as unqualified had 11 years of experience as a deputy attorney general and many more years in private practice.
General background on the process and its history can be found here.
It gets harder to analyze the cases as you go further back in history, because the nature of the position and the nature of what it means to be a lawyer have shifted a great deal.
For example, while there was somewhat organized legal instruction very early in U.S. history on an isolated basis, the modern law school model pretty much dates to the 1870s. Instead, most U.S. lawyers would "read law" as an apprentice to an experienced attorney.
Also, many federal judges and members of Congress in the early period didn't serve for long because other positions were more prestigious when the federal government was comparatively unimportant.
For example, Powhatan Ellis who served as a federal district court judge for Mississippi (chosen at random) had four years of experience as a lawyer in private practice from 1813-1817 (he started his private practice a year before finishing his legal education), then served on the Mississippi Supreme Court for eight years from 1817 to 1825, then served six of the next seven years as a U.S. Senator (1825 and 1827-1832) when that position was appointive, then served as a federal district court judge for four years (1832-1836), then served six years as a diplomat to Mexico (1836-1842), and then spent his next twenty-one years until his death as a lawyer in private practice, first in the United States and then in the Confederate States of America. Assuming that time as a judge counts as time spent practicing law, he had twelve years of experience before serving as a U.S. District Court judge, but the circumstances in the pre-modern period are hard to compare to the situation today.
I have not located anyone appointed to the federal bench with less experience at a lawyer, at any time, and no one close in modern history.