Final answer:
The first NHL team to allow 400 is unclear due to lack of context, such as whether it refers to 400 goals in a season or another statistic. Without additional information, we cannot accurately identify which of the listed hockey teams was the first to allow 400.
Step-by-step explanation:
The question "What was the first team to allow 400?" appears to be related to a historic milestone in professional ice hockey, specifically the National Hockey League (NHL). As the question stands, it lacks context, making it difficult to deduce whether it pertains to a team allowing 400 goals in a season or some other statistic.
None of the listed teams (New York Rangers, Toronto Maple Leafs, Chicago Blackhawks, Boston Bruins) have a recorded history of allowing exactly 400 goals in a regular season; thus, the question might be misphrased or missing specific details.
Statistical records do show that teams have allowed large numbers of goals in the early years of the NHL when seasons were shorter, and defense was less sophisticated.
Without additional information, it is not possible to identify which team reached the described milestone first. It is recommended to seek further clarification on the question, looking for the specific record or statistic in question.
Should further details emerge that specify the statistic, such as goals allowed in a season, a more definite answer could be provided after consulting verified historical NHL records.